Guren Ichinose

Guren Ichinose (一瀬グレン) is the main protagonist of the prequel story Seraph of the End: Guren Ichinose: Catastrophe at Sixteen and its sequel, Seraph of the End: Guren Ichinose: Resurrection at Nineteen light novel series. In addition, he is the tritagonist in the Seraph of the End: Vampire Reign manga series, which takes place eight years later.

With the death of his father, Guren became head of the Ichinose family, when he was still 16, and remains head of the family as an adult. Guren is a Lieutenant Colonel of the Japanese Imperial Demon Army and the leader of the Vampire Extermination Unit's Moon Demon Company. He is also the squad leader of the Guren Squad (グレン隊), and has been since his teen years.

Appearance
Guren is a tall, young man with medium length black hair parted in the middle and purple eyes.

Catastrophe
He wore the First Shibuya High Uniform, a black gakuran with a standing collar, with red trim which was also around the cuffs. Instead of the school emblem, Guren wore the Order of the Imperial Moon emblem on the left breast.

When his squad was first formed, he wore the standard JIDA uniform which consists of a long-sleeved black jacket with two rows of gold buttons on the front and red details including the shoulder epaulets. A brown Sam Browne belt passes diagonally over his right shoulder and holds a brown pouch on his left side. Along with that, he wears a pair of white gloves and a red standard belt. He also wears the uniform trousers with knee-high black boots which goes over his trouser legging.

Vampire Reign
He sometimes is shown with his hair slicked back during the midst of skirmishes on the battlefield, but more often is seen with slightly tousled hair, with bangs hanging over his forehead. He wears the standard JIDA uniform, which consists of a long-sleeved, double-breasted black coat with two rows of gold buttons down the front, red details including shoulder epaulettes, gores at the bottom, and stripes on sleeves. Other decorations include gold aiguillettes and white fourrageres worn on the right shoulder, attached to a stylized cherry blossom decoration pendant at the center of his collar, and two bars with unit insignia medal below them on the left. He wears a pair of white gloves, a black on white armband on his left arm, and a similarly striped black and white web belt with a frog for his sword on the left, and a gold waist-plate. In addition, he also wears the uniform trousers with two white belts strapped around his left leg and black shoes.

In the manga illustration, he also wore a black cape or overcoat with a red lining, and in the anime's artwork, he is shown wearing a maroon coat with red ornamented sleeves. Anime and manga versions have in common shoulder epaulettes and a gold unit insignia. While the shoulder epaulettes are primarily red in the anime, they are a mixture between black and beige in the manga. The anime version shows extra red markings and gold details. In contrast to the anime, the manga depicted the cloak to have beige for its insignia, and details spread all around the garment, with no markings visible.

Human
Guren was naive in his childhood days where most of his time was spent with Mahiru Hīragi. His outlook on life was simple while his life was only happy moments. When he was forcefully separated from Mahiru and treated with contempt for being part of a lowly branch family, Guren felt guilty for being too weak in physique and power to not reach out for what he wanted: Mahiru. Motivated by Mahiru to become stronger and wiser, Guren would become a wise leader who values teamwork, cooperation and friends, determined to ensure the survival of the human race from demons and vampires. When Yūichirō Hyakuya tried to join the Moon Demon Company, Guren refused until he made friends.

Guren sometimes pretends to be lazy, but in truth, he really works hard. He keeps many secrets to himself, and has no difficulty lying about them. He also plans to dethrone the Hīragi Family; however, this is shown to be explicitly desired by him upon being possessed by Mahiru-no-Yo. It is made clear when Guren is possessed, and his true desires come to light, that he, along with Shinya Hīragi, wants to change the status quo and hierarchy.

In addition, he actually cares a lot about his subordinates and friends, considering them to be his family, both before and after the apocalypse.

In the past, as shown in the Catastrophe light novels, he was strongly devoted to his lover Mahiru Hiragi, showing the strength and goodness of his heart, staying true to his love for Mahiru and desperately keeps trying to save her, even when she was turned into a vampire and then when she was demon, also rejecting his female companions due to his devoted love to her. Indeed, even when pressured with the death of Sakae, Guren showed he couldn't bring himself to actually kill her, opting to commit suicide with her, which failed. Even after Mahiru killed all his friends, Guren forgave and tried to save her as she died. Her death was so devastating to Guren that he even asked Ferid to kill him. Although he treats Mahiru-No-Yo coldly, as later on revealed he never let go of the guilt and sadness he felt over his failure and despite having been willing to trigger the Apocalypse to save his friends, he shows regret over what he had done to the world, which ultimately motivated him to become a demon to atone for his mistakes.

Namanari
His kindness is the reason for why he hasn't been completely honest with his squad whenever they're around him, especially hiding from them his second personality, which Kureto knew of all along, and later Shinya became aware of. It was another reason for why Guren's original personality had yet to be fully taken over by his second, demonic personality, and continues to exist. Nevertheless, he has since kept his own emotions in check on a daily basis, carefully maintaining a positive image so not to worry them.

Guren's personality changes drastically when he's overtaken by his demon blade, Mahiru-no-Yo. According to Ferid Bathory, it happens more often than shown, and his demon side is capable of hiding his true nature from his close friends. Guren is described as being a Namanari, a human with two souls in his body, just a single step away from becoming a complete demon. When Mahiru is in control of Guren's body, he becomes utterly ruthless in the pursuit of his goals and cuts down anyone who opposes him, even if it is one of his comrades, like Shihō or Yu. He doesn’t distinguish vampires or humans as friend or foe to him when possessed, but sees them all as only sacrificial pawns for the Seraph of the End experiment.

Kureto considers the demonic personality to be strong and the original human personality to be weak.

After Mahiru-no-Yo and Noya separate, truly turning Guren into a Namanari, Guren has shown previously unseen lenience by sparing Shinya and the rest of his squad, showing he still cares for them but will not hesitate to put them down when needed, as he ruthlessly pinned down his squad and brutally attacked Shinya until he could no longer try to stop him and drained power from the rest of his squad to prevent them from attempting anything.

History
Guren was born into the Ichinose family, a low branch of the the Order of the Imperial Demons that's ruled by the Hīragi Family whom they despised. He was also the best friend and childhood partner of Mahiru Hīragi, but this was frowned upon by the higher-up members of the Hīragi family because of his family's lower social status.

Guren was blamed for becoming too close to her because of their friendship, and the consequences to him were many harsh beatings by adults and teenagers from the Hīragi family during his childhood.

The bad treatment towards him and the Ichinose family motivated Guren to train harder and become stronger while growing up, with a stronger sense of determination. It inspired him to volunteer as a subject of a Kiju experiment for the sake of his family, to obtain an advantage over the Hīragi family.

Events of 2012
In April, a teenage Guren and his bodyguards, Sayuri Hanayori, and Shigure Yukimi, head to First Shibuya High School. Because the Ichinose Clan is looking for an opportunity to overthrow the Hīragi Clan and not wanting to give away any of the Imperial Moon's abilities too soon, Guren makes himself look weaker than his retainers and acts like a slacker to hide his true skills and power; thus, he lets himself get soaked by cola that a student throws at him and get hit by a lightning spell by another with short, white hair. Guren has Shigure leave to get clean clothes and goes into the school.

During class, Guren is placed in Class 1-9 along with other students from high ranking clans, though there is one name that catches Guren's eye: Shinya Hīragi. Said Hīragi arrives late, and turns out to be the white haired student that attacked Guren earlier with the lightning spell. Shinya ends up taking the seat next to Guren, and reveals that he wants to help Guren bring down the Hīragi Family. During the entrance ceremony in the auditorium, a crimson red haired girl gets Guren's attention during the principle's long opening speech, and Guren figures out she is from the Jūjō Clan. After some snide words were exchanged, he learns the girl's name is Mito, and even antagonizes her enough to raise her voice to shrieking that it interrupts the principle's speech, embarrassing her in front of everyone. After some time, Mito asks Guren a question regarding Shinya, having noticed their conversation in class, which Guren lies by saying that they were talking about girls. When Mito mentions Mahiru, Guren gets reminded of how he found out about Shinya and Mahiru's engagement later than the public more likely as a result of his father trying to keep him from ever finding out about it. Eventually, the principle finishes his opening speech, and Guren sees a teenage Mahriu again, after ten years separated from each other, give her speech as this year's class representative. Later that evening, Shigure and Sayuri move themselves into Guren’s apartment against his wishes. While taking the elevator to the training room, he encounters a well dressed man, whom Guren thought at first was the land lord heading to the floor two levels above the training room; however, upon seeing the floor button wasn't pressed, Guren realizes the man was an assassin. He attacks him with his family blade, Kujakumaru, but the man is able to hold his own against Guren with chains that are enchanted with what seemed to be Western based magic. Guren then slices into the man's body which hits chains instead of bone and releases a black poisonous mist from his body that begins to fill the elevator. Seeing Guren not succumbing to the black mist, the man complements him which leads the two to go back and forth until Guren asks the man if he is a chimera, a human experiment, which the man confirms and introduces himself as Makoto Kijima, a member of the Thousand Nights. After calling back the chains and the black mist, Kijima says he came to offer Guren to join the Thousand Nights in eliminating the Imperial Demons which Guren refuses. At some point the elevator doors opened allowing Guren to get out and was charging up his blade's curse when the elevator doors close.

Guren soon settled into a routine at school that was putting up with the bullying and hiding his true strength, and one day during sparring practice, Guren allows himself to get beaten by Norito Goshi, a boy who is also in Guren's class. He gets berated by Mito for losing that easily, and then Shinya comes in to spar with Guren. He punches Guren in the chest so hard that he breaks several ribs and is coughing up blood before losing consciousness. Mahiru visits him in the nurse’s office, and despite finally having the chance to talk to her for the first time in years, it ends up becoming awkward with Guren treating her coldly.

The next day, Guren continues pushing Shinya away and refusing to reveal his true strength. When he shows submissiveness to Seishirō Hīragi, in spite of the latter having kicked him to the ground and beating up Shigure for trying to protect him, Guren ends up losing what little respect he has from everyone in the class, including Shinya and Mito.

Guren encounters Makoto Kijima for the second time, but a young boy named Mikaela addresses the man as "Mr. Saitō." After Saitō reveals that the Hīragi Family is involved with forbidden magic and that there will be an attack in ten days, Guren sends a message to his father about it.

It is the time for the qualification exams, where the students fight students of other classes one-on-one in a tournament-style battle. Guren fights as poorly as possible and wins by "accidentally" hitting his opponent with a wild swing that knocks him out. A few days later, Guren forfeits his match against Seishirō, which leads the whole school to mock him until the Brotherhood of a Thousand Nights attacks and kills many students and teachers. Guren is able to save Mito and Goshi from the attackers before fighting Saitō alongside Shinya, where they learn that Mahiru betrayed the Hīragi Family.

Mahiru then appears and attacks Guren with a black katana which leads to the two to fight. Mahiru then reveals to Guren that the weapon she's wielding is a successfully made demon possessed weapon known as Cursed Gear; she claims that the combination of Hīragi and Thousand Nights magic have made it possible to make contracts with high class demons. Mahiru then cuts herself off and struggles against herself to warn Guren not to listen to her. When Saitō tells Mahiru they have to leave, Guren lunges at him, only for Mahiru to get in the way and cut his sword, Kujakumaru, in half.

After the Order of the Imperial Demons announces it put down the "terrorist group" that attacked them before, the school reopens. Shinya helps Guren get drenched in cola again when Shigure nearly stops the attack. Mito and Goshi become friendly with Guren, Sayuri, and Shigure. In another day of school, Mito tries to train Guren on fighting and Norito tries to comfort him which Guren brushes off both of them. Shinya then comes along and is able to gain Guren's attention when he reveals what the Hīragi Family knows. Guren learns that stops due to Kureto Hīragi watching them from above.

After a day of school, Guren encounters Shinoa Hīragi, who delivers a message to him from Mahiru. When Mikaela and Akane Hyakuya arrive, Shinoa pretends that Guren is a pervert, and Mika moves to protect her and threatens to call the police on Guren before Guren scampers off.

Shinya, Mito, Norito, and Guren leave to continue their examinations in the gym. When Guren arrives for his bout, Kureto questions him about the Thousand Nights and then attacks him with the intent to kill, forcing Guren to fight seriously.

Under torture, Guren reveals that the Thousand Nights contacted him. Under the threat of having the entire Ichinose Clan destroyed, Guren agrees to become Kureto’s underling.

Guren learns that something involving the Thousand Nights is occurring at the Ueno Zoo. He returns to school and learns that rumors spread about him being Kureto’s lackey. Seishirō confronts him. A few days later, Guren, Shinya, Mito, Norito, Sayuri, and Shigure report to Kureto’s office, where Aoi Sangū lets them in. Kureto orders them to investigate Ueno Zoo and Guren leads this new team.

The squad enters Ueno Zoo and battles a chimera made with genes from the Four Horsemen of John. Mahiru lends Guren cursed gear, which takes him one step away from humanity and causes a demon to sprout inside him. Ferid Bathory out-matches them without any effort and takes half of the chimera with him.

Guren wakes up after being in a coma for one month, and Sayuri confesses her love to him. Ten days later, he returns to school.

Iori Mitsuki, a curse researcher working for the Ichinose family, draws black blood from Guren's arm. She informs him that all of the researchers are looking into his case, and he appears to have traces of an unknown man-made poison in his blood with curses mixed in.

Guren recalls when Mahiru infected him.

Mitsuki requests permission to perform human experimentation using a few devoted believers, even though that is forbidden within the Ichinose by the Mikado no Oni under the Hīragi. Guren does not permit it and says he will be the subject instead. Should the Ichinose perform human experimentation, the Hīragi would interpret it as a declaration of war and would annihilate the Ichinose.

Since she is unable to accept using Guren as an experimental subject and they both have type-A blood, Mitsuki injects the black blood into herself and insists on using herself as the subject first. After a few seconds, she begins screaming and loses control as she begins turning into a demon. Guren uses the demon sword, Hakushi, to cut off the transformed left hand. The severed hand grows and mutates, sprouting eyes, teeth, and appendages until it is larger than a human. When it attempts to devour Mitsuki, Guren attacks and kills it.

Mitsuki stops the bleeding with talismans, and researchers rush in. Despite losing her hand, she smiles and says the sacrifice is worth it. The other researchers agree, and Guren tells them they must minimize the experimentation to hide it from the Hīragi. He tells them they must complete this within four months because of the upcoming Apocalypse on Christmas.

When Guren leaves, Shigure and Sayuri approach him and demand to know what he is hiding from them.

Rumors about Guren hiding his strength flood the school. During class, Shinya sidles over to Guren and begins whispering to annoy him. He then passes a note to Guren revealing that the Thousand Nights is planning to meet at 2:00 a.m. the following morning at the tennis courts in Hikarigaoka Park. Guren wonders whether he can trust Shinya. They begin talking about Mahiru, and Shinya says he admires her and is jealous of Guren. Guren carefully pockets the note while being sure to preserve Shinya’s fingerprints.

After class, Kureto calls Guren. Goshi asks if it is Guren's girlfriend on the phone, surprising Mito. Kureto orders Guren to go to the student council room during lunch tomorrow. When Shinya asks if that was Kureto, Guren says it was his girlfriend, causing Mito to become even more flustered. Guren walks off without explaining the joke, but Shinya takes pity on Mito instead.

Guren meets with Shigure and Sayuri. Goshi says they should all go to Guren's house to play, and Shigure asks if she should kill them. The group chats as they walk, and Mito says she will support Guren until he acquires the status he deserves. Guren wonders if he has the heart to kill Mito and Goshi when the time comes.

In Guren's condominium, Shinya is defeating Mito at shogi while Goshi and Guren watch while the 6 pm newscast reports at the scene of a fire. Although none of them knew how to play shogi, Goshi insisted on them buying a cheap game from the convenience store. They played in an elimination-style tournament against each other. Goshi easily defeated Guren in the first round, and Shinya is winning the second. As it turns out, Guren felt drained at the start of his match and lost on purpose, delighting Goshi and causing Mito to comfort him. However, Shinya realized it, annoying Guren evermore. When they tease Mito, she tells them the TV is distracting her.

They all end up watching the news coverage when a disheveled woman in her mid-twenties with long, silky black hair appears from the crowd and gets into a confrontation with the firefighters in order to get to her son, Yuichiro. She attempts to set herself on fire while screaming that the fire should never be put out and calling the boy a demon child that she needs to kill. A man then approaches the camera, who Guren recognizes is Saitō upon catching a glimpse of his face, before the footage at the scene cuts out.

The three soon decides to leave with Mito hungry and Shinya having to do something, and Guren notices that Shinya had left his phone on the floor. As soon as they are out of the apartment, Guren looks into Shinya's phone, finding that it was opened to email and that a funny message was written for him, but the phone did not contain any useful information.

Shinya comes back, and confirms to Guren that he left his phone on purpose and that the former knew that the latter lost to Goshi on purpose. When it came to the meeting with the Thousand Night, Guren says they should not go investigate since it is too dangerous, and instead should investigate the fire first. Shinya tells him to not lie to his comrades, and Guren informs him that Shinya is not his comrade.

Mito and Goshi come for Shinya, and the three leave again. There are no longer any news reports of the fire, meaning it was most likely censored by the Thousand Night. As Guren ponders what to do, Shigure and Sayuri return home. He decides to investigate without them. Guren arrives at Hikarigaoka Park at 1:30 a.m. the next morning, shortly before Shinya. They sneak into the park and get into position to watch the tennis court. They see eight trained Thousand Night men in suits. The men yell something and then get into battle formation. The men launched chains from their bodies at a vampire, who easily avoids their attacks while decapitating three of them and drinking the blood of a third. Within seconds, the vampire kills the rest of them. She does not appear to be a noble.

She glances at Guren and Shinya and smirks.

Guren and Shinya immediately race to their motorcycles. Guren runs his motorcycle into her, but she easily catches the motorcycle and pops its tire. Guren swings his sword, and Shinya grabs Guren as they flee. They crush a taxi, and Guren throws exploding tags at the pursuing vampire. One blows off her foot, but it rapidly regenerates. She ignores the fact that her clothes are on fire and continues to chase them.

Despite going as fast as they can, she easily catches up to them. Guren cuts off her hand. Unperturbed, the vampire watched them escape. They dodge around traffic but break a rearview mirror, which hits Guren in the forehead.

Since she is no longer chasing them, Guren tells Shinya to slow down. Shinya says they will be arrested if he does that because Guren is waving a katana around and not wearing a helmet. Guren says he does not want to die because of inferior driving ability. Shinya eventually slows down, and they pull into an alley.

Guren wonders about why the vampires have become so active lately. He considers that Mahiru might be instigating all of it.

Guren thanks Shinya for saving him and says he trusts Shinya a little more. They split up to head home.

Over three hours later, Guren returns home and is greeted by a panicking Shigure and Sayuri. They begin crying. He reminds them not to touch his blood. He orders them to go to Aichi for a check-up. He feels relieved he left them behind because they would have been killed by the vampire.

Guren takes a bath and finally collapses into bed after 4 a.m. but is unable to sleep.

The next day, they attend class, and Guren wins four out of seven matches against Shinya until they are crushed by another student who is skilled at shogi.

During lunch, Guren takes his katana and meets up with Aoi Sangu, who leads him to the gymnasium basement where Shinoa Hiragi is bound. Her fingernails have been torn off, and her face is covered with bruises. Guren makes an expression of disgust, Kureto comments about it, and Guren says he hates torturing kids. Kureto agrees but says such things do not matter for a Hīragi.

Kureto asks Guren about the Thousand Nights meeting and asks if Mahiru is the traitor. Guren remains silent before eventually saying he does not know. After a few more questions, Guren says he does not know if Mahiru is the traitor. Kureto continues asking him questions, and Guren keeps denying his accusations.

Kureto says that the messenger sent by the Thousand Nights did not survive. He glances at the neighboring room, which has blood seeping through the walls. Guren comments about letting a child see that. Kureto comments that the Ichinose are gentle and appreciates how Guren knows he cannot win against Kureto.

Guren walks over to Shinoa, pats her head, and releases her restraints. She asks permission to stand up, but Kureto orders her to remain seated.

Kureto reveals that this is actually all makeup and Shinoa was not actually tortured. He says she would not reveal anything anyway.

Kureto says this was all to gather information and says he will trust Guren. Kureto says he already knows Guren met Shinoa, so he will kill Shinoa first. Kureto grabs Shinoa by the neck, and Guren charges him. Kureto blocks his attack and threatens to break Shinoa's neck.

Mahiru sends Kureto a message telling him to do as he pleases, and tears briefly form in Shinoa’s eyes. Kureto talks about Mahiru and says Guren is the opposite of her. He says Guren is idiotic trash being used by that woman. He calls Mahiru a beautiful monster. However, he says that Mahiru might listen to Guren. He Kureto wants Guren to give Mahiru a message if he encounters her. He says he will permit them to marry because he wants to keep her in the family. He advises Guren to hold her and never let her go or else kill her before she destroys everyone around her.

Kureto sends Mahiru's IP address to Guren. He orders Guren to meet and persuade Mahiru. Guren asks whether Kureto or Mahiru is stronger, and Kureto tells him Mahiru is stronger. Guren follows orders to immediately send a message to Mahiru.

After a moment, Guren's phone rings. He answers it, and Mahiru is on the other end. She asks to speak with Shinoa. Under Kureto's orders, Guren puts the phone on loud speaker. Shinoa reports that everything went as expected. She reports that Guren, Kureto, and Aoi are listening to their conversation. When she asks about their father, Kureto reports that he does not know she is missing. She calls him a liar and accuses Kureto of her crimes, saying he actually did everything instead of her out of jealousy. He says no one will believe her. After they talk for a bit, she mocks Kureto for prolonging their phone call to track her instead of hanging up immediately.

He says he found her, but she informs him that his special ops are already dead.

A student suddenly enters the room and reports that Kureto's conversation is being broadcasted across the entire school. Guren notices a sound-muffling talisman at the edge of the door.

Kureto orders Guren to end the call, but Mahiru says many students will die again. Kureto takes the phone and turns off the speaker. He says she is going to cause innocent deaths. She continues to place blame on him. Kureto orders a meeting to sentence the traitor, Mahiru, before hanging up.

Kureto asks Guren if he knew about any of this, but Guren deflects the question. Kureto decides that Mahiru single-handedly pitted the against the The Thousand Nights.

Kureto thinks and talks some more. He says that Guren is a human, not a monster like Mahiru, and tells him to become his comrade. He wants to solve this situation with as few casualties as possible. Guren states he does not have a choice.

Today’s date is August 21st.

Kureto releases both Guren and Shinoa. They encounter Shinya in the gymnasium, and she shows off her interrogation makeup to him. She and Shinya joke around, so Guren walks off.

Shinya reports that the students listened to the broadcast in silence. Afterward, the students begin discussing the announcement.

Guren asks Shinoa how she feels about her sister. She says Mahiru would be the one most against her death while no one else would care at all. When Guren and Shinya both say they would be sad if she died, she says they only care about her as a replacement for her sister, whom they love so deeply.

Shinoa states it is clear Mahiru officially abandoned her today and will probably never contact her again.

Guren wonders about Mahiru's actions and the war that will ensue. The site where his arm was cut off and reattached in a previous novel causes him pain.

The bell for fifth period rings, and Shinoa holds out her hand to request money from Guren. She says she was kidnapped too suddenly to grab her wallet and wants to take a taxi home. He says he is not interested in caring for Mahiru's little sister, but she and Shinya laugh. Shinya gives her a 10,000 yen bill and asks her to ask Mahiru if she remembers who her fiancé is.

Mahiru calls Guren again, and he steps away from Shinya and Shinoa to answer his phone. She speaks softly and says that no one is eavesdropping on them. She says she only wanted to hear Guren's voice. When he says she was fooling around with him only a moment ago by asking if he were still alive, she says the demon was in control. Since she cannot prove she is not a demon right now, he says he will end the call, but she says they may never be able to speak again. Although he believes he should hang up the phone, he cannot. She asks him to kill her while she is still able to resist. He says he will help her control the demon instead, but she insists he kill her on sight. He hears her crying. They establish a rendezvous later at 5:30 p.m in apartment 501 located fifteen minutes from Ikejiri-Ohashi Station. Guren reads about the demon experiments ongoing in Mahiru and Shinoa. Mahiru does not arrive until 7 p.m.

Guren draws his sword and asks if she knows they were supposed to meet today. If not, this would be the demon. She laughs and asks if he thinks he can kill her. Guren asks the demon where Mahiru is, but she says she is Mahiru. She says she desires Guren, and Guren tells her to shut up. He moves the curtain standing between them. Mahiru has tears in her eyes. Seeing Guren, she makes a painful expression and backs away, but Guren grabs her wrist and embraces her. She squirms and says she no longer has the right to be with him. He says they are together now. She buries her face in his chest and cries.

She says it is impossible to save her, but he disagrees. When she asks him if he still loves her, he hesitates to answer because he feels like loving her may be the same as betraying his comrades. She was his everything ten years ago. Guren calls himself an idiot, and Mahiru says she loves him the most. She calls herself a monster, and he kisses her. He embraces her, and they have sex that evening.

Mahiru gets up from the bed and gets dressed. She fondly looks at Guren and remembers their childhood. Guren asks if she is leaving. She says Guren cannot protect her, and the ones he wants to protect are his comrades. She says that if he loves her and wants to be with her, he must kill all of his comrades, but he cannot do that. She tells him he is very gentle. She says protecting his comrades is dashing but will not make him strong.

She reveals that she engulfed Shinoa's demon and now has two demons running rampant within her body, speeding up her degeneration. She says giving her virginity to Guren was her dream, so now the six-year-old her can rest in peace. She says she is now a demon, but Guren says he cannot believe her when she has tears in her eyes. She tells him he cannot give up everything to run away with her.

She says she shared part of the demon with him in order to fully remove it from Shinoa, so he will become a demon as well. She apologizes to him. He asks to fight side-by-side with her, but she says there is not enough time left.

Guren asks if the Thousand Nights is going to release some kind of virus, and Mahiru laughs.

The vampire from last night appears at the window, greeting Mahiru Hīragi for the first time. Nonplussed, Mahiru calls upon Asuramaru and cuts the vampire in half, turning her into ash.

Mahiru asks Guren if he were scared by the vampire yesterday. She reveals she fabricated information to set the Hīragi House and Thousand Nights against each other. They hear the sounds of explosions. Mahiru says she became a demon in order to stay by his side, but he refuses to let her give up her humanity. She asks them their age and jumps out of the window. Guren realizes they are sixteen, which is too old to survive the virus.

Sayuri calls Guren and tells him to escape now. She mentions the Thousand Nights before the phone disconnects. Guren is unable to contact either of his aides. Mito calls him and says she is trapped in the audio-visual room with some other students. She thanks him for treating her like a normal girl instead of an heiress and tells him not to come. She tells him she loves him. She says there are blood and enemies everywhere and that Goshi, Sayuri, and Shigure protected her. She says the door is being forced open and asks Guren to save her. Guren hears an explosion, and the phone disconnects.

He curses and runs. In an alley, he comes across a running motorcycle with no owner and a demonic sword. Guren feels tired and laughs. He says that, like Mahiru, he will turn from a tortoise to a hare and become a demon. He says he will give up on his humanity because he does not want to give up on anything.

Guren calls Kureto and reveals his location. He says Mahiru killed the Thousand Night members. He asks Kureto to kill him if he loses control during this experiment.

Guren then calls Shinya and reports to him that he had sex with Mahiru. Shinya says he feels horrible after hearing that. He says he accepted the demon and is going to school to save his comrades. Shinya calls him an idiot. Guren says he will leave Mahiru to Shinya if he dies. When Shinya asks if he wants him to marry her or kill her, Guren hangs up.

Guren grips the demonic sword, and darkness overcomes him. His catastrophe begins.

Guren Ichinose contemplates what he should do while facing imminent failure: 1) give up, 2) keep trying anyway, or 3) fight to fulfill your ambitions and risk losing everything else. Guren chooses option three. He is filled with desire and despair. In a small alley, he risks his humanity and grasps the demon weapon Noya. He senses the Apocalypse begin.

Guren hears a voice calling his name and awakens in a completely white space in his heart. The demon Noya tempts him with power and approaches him. He chats about Mahiru and says that Guren will turn into a demon regardless of whether he accepts that power or not. Guren touches Noya and willingly gives up his humanity, leading Noya to mock him for making the wrong choice. He says it is unacceptable for a human to give up on his humanity while he is still human. Everything goes black, and power overwhelms him.

Guren wakes up with the sword in his and a motorcycle next to him. He hears war going on all around him but no longer feels any pity or empathy. His desires encourage him only to kill, and he mutters about needing a sheath to suppress the demon's will before getting onto the motorcycle and heading to school.

Guren goes to the battlefield at the school and kills many Thousand Night members. Shigure notices Guren's sclera have turned black. The two aides notice something is off about Guren's behavior, and he warns them not to come near him. He struggles against his lust for violence and his lust for Sayuri's body.

Saitō applauds Guren's success. When Guren tries to kill him, Saitō uses illusions to mislead his attacks. He tells Guren to fulfill his desires and says that Goshi is in the fifth floor girls' restroom while Mito is in the audiovisual room. He says that Guren's success in this state will give him such pleasure he will truly become a demon.

Mahiru arrives and mentions that Guren had sex with her earlier. She does this to emotionally hurt Sayuri and Shigure and subtly weaves illusions around them in order to tempt them with the offer of a demonic blade. She goes after Sayuri first, but Shigure notices the illusions and tries to warn her.

Guren attacks Mahiru, and Mahiru throws the cursed gear at Sayuri. Guren protects Sayuri from it, but it gashes open his left hand, infecting him with even more demonic influence. His blood bleeds black. A single horn protrudes from his head, and his sclera become black under the demon's influence. He howls in pain.

Pleading with Guren and desperate to get him from Mahiru, Shigure begs him to kill her first. Then, Sayuri joins in. Guren regains control and attacks Mahiru, stating it will not go as she plans.

Mahiru and Saitō leave. Sayuri and Shigure beg Guren to come with them to Aichi, but he runs inside the school to save Goshi and Mito instead. A blood-coated Guren steps into the restroom, where Goshi is hiding and kills all of the Thousand Nights members inside. Goshi notices something is wrong with him, and Guren begins asking for blood. Guren fights the urge to kill Goshi or to tell Goshi to run. Guren eventually retreats and continues slaughtering everyone in the hallways.

Goshi chases after him. The demon's euphoria grows each time Guren kills people and saves his comrades. Guren continues struggling against Noya and is aware of Mahiru's spells increasing the desires of everyone in the school.

He finally reaches the audiovisual room and finds Mito crying in the hands of Thousand Night soldiers. Mito feels relief, and Guren slaughters the Thousand Nights members. With tears in her eyes, Mito collapses into Guren's arms. Noya encourages Guren to kill, destroy, and rape.

Guren rips open Mito's blouse and kisses her. Guren manages to briefly break the demon's control and pushes her away while yelling at her to get away from him. Mito is shocked but notices Guren's horns and pointed teeth.

Guren struggles against the madness to kill and punches himself in his face. Mito says she wants to save him, but Guren warns her it is too late. The demon speaks through Guren and says he does not regret it. He says he became like this because he likes Mito. Guren says it is the demon talking. Then, the demon says Mito can save him by taking off her clothes and kneeling for him. He tells her to embrace him and attend to his needs.

Mito falls to her knees, and Noya overwhelms Guren. He approaches Mito and raises his sword. She says she will not resist if killing her will relieve his pain a little. Before Guren kills her, Goshi detonates an explosion tag on his bag. Using an illusion spell, Goshi escapes with Mito. Mito struggles, but Goshi helps her understand the situation.

Guren tells him they cannot come back and rescue him because they will die here.

Goshi and Mito escape to a balcony and jump to the ground. Guren chases them, struggling with the desire to kill them and the despair of being unable to save anyone. Guren's sword nicks Goshi's face but stops short of any serious damage. Guren takes control again and tells Gosh to not come back. Noya takes control again.

Shinya fires missiles of powerful talismans at Guren and allows Goshi and Mito to flee. The soldiers keep firing the talismans at Guren, and he retreats into the audiovisual room. The talismans cover the balcony and then the keep firing in order to seal him within the school. There are no signs of life because he already slaughtered everyone still inside the school.

Guren feels that he has been saved. Relieved with the idea that there is probably enough research done on the cursed gear by now for the Imperial Demons to kill him, Guren sighs and the curses advances once again.

Mito and Goshi narrowly escape while Imperial Moon soldiers seal Guren within the school. In exchange for saving Guren, Sakae says he will hand over the Ichinose’s research to the Hiragi and will accept any punishment.

Guren sits alone in a dark classroom. Noya went to sleep about an hour ago, and it is now 2:40 a.m. Guren wonders if the evolution of his desires is part of the process of bonding with the demon.

Mahiru calls him, but he ignores her call. She texts him, warning him to pick up before she kills everyone precious to him, and he finally picks up the third time she calls. He tells her he hates her, but she says she is the only one who can understand him now. She congratulates him on maintaining his consciousness much earlier than she did. She says mankind will progress the cursed gear research to about 70% but will then stop due to safety precautions. Guren tries to coax the human part of Mahiru awake, and she eventually says his name and then hangs up. He tries to call her back four times, but she does not answer.

Light enters the classroom as the talismans are removed, and Shinya arrives with Mito, Goshi, and nine other soldiers. They all have demonic blades equipped to them.

Noya wakes up, demanding murder.

Shinya, Goshi, Mito, and Guren struggle against Noya. Thanks to the cursed gear, their injuries heal unnaturally fast. Shinya tells Noya that the humans have already found a way to turn demons into their slaves. They fight, and Goshi uses an illusion to distract Guren while Shinya pastes a weakening talisman on Guren's neck and hugs him. The troops pierce Shinya and Guren with wooden stakes, and chains wrap Guren to Shinya from the feet on upward. Guren loses consciousness.

Guren meets with Noya in his mind. The chains bind Noya and weaken him, pulling him into the ground. Noya warns Guren that his allies will betray him, but eventually he says that he will patiently wait until Guren joins hands with him.

Over an hour later, Guren opens his eyes in the classroom but is too embarrassed to start talking right away. Shinya teases Guren about thanking him. Mito and Goshi are so relieved that they have tears in their eyes.

Guren asks about the cursed gear research and the Thousand Night's movements. They chat a little, and Guren and Shinya reveal to Mito that they were fighting over a girl. Guren says he won, but Shinya says Guren got dumped afterward. Mito is shocked and then a little happy after finding out Guren got dumped.

Not seeing Shigure or Sayuri, Guren calls Kureto. Kureto says they are in the office and tells him not to call them before hanging up.

Guren goes to Kureto's office. Kureto says he overheard Guren and Mahiru's phone conversation. Kureto has a cursed gear weapon with him but has its power completely under control. He and Guren agree that they need to keep their rationality and numbers in order to fight stronger berserker-type opponents controlled by their cursed gear, such as Mahiru.

Kureto attacks Guren and overwhelms him, leaving Guren to wonder if Kureto specifically used charms on Guren's weapon to make him weaker than Kureto. Kureto says that all of the people serving Guren have been given the death penalty, and Guren attacks him but is no match without unsealing his demon. Kureto says Guren's weakness is that he becomes shaken when anyone riles him. He says that he is actually protecting all of Guren's family and subordinates.

Kureto says he is protecting them because he wants Guren, but Guren believes Kureto is doing this to step out of Mahiru's control. Being a Hiragi, Mahiru would assume that all of the Ichinose would be killed, so he believes not killing them would be outside of her expectations.

When Kureto says Guren's subordinates willingly became guinea pigs for the experiments in order to stop Guren's demonic possession, Guren grabs Kureto's collar. Several soldiers surround them and draw their blades, but Kureto stops them.

Kureto reveals that Tenri Hīragi reached an agreement with the Thousand Nights, and both groups will work together on producing cursed gear. However, Mahiru holds key information and must be removed from the equation. She is far too dangerous.

Kureto orders Guren to kill Mahiru. If he does not kill her within one month, Kureto will have Sakae Ichinose killed. If he does not kill her after another month, Kureto will have 100 of Guren's subordinates killed.

Guren leaves. Mito, Goshi, and Shinya overheard his conversation with Kureto and try to comfort him. When Guren denies having companions, Shinya disagrees and tells him to take responsibility and lead their squad. All three hold out hands to him. He takes their hands and calls them tiring. They laugh.

On, September 2nd, Mito, Shinya, Goshi, and Guren play video games at Guren's place while Sayuri prepares food. Unless Mahiru is killed, Sakae will be executed in eighteen days. Guren is spending time with friends in order to help resist the demon in his heart.

Mahiru comes to his apartment shortly after 8 p.m. and has black eyes. Guren faces her alone. He stabs her through the shoulder and jumps from the twenty-fifth floor with her. She does not resist. He says he does not have the will to stab her in the heart, but he can at least die with her. Her eyes return to normal, and she slows their fall with her sword. She throws Guren back into the wall to save him, and he is badly injured. She continues falling and breaks her leg, but it heals almost immediately.

Twenty soldiers attack Mahiru on the ground, but she kills them easily and leaves. Guren returns to his apartment and examines the documents Mahiru left him. He reads about the Seraph of the End plan being conducted by the Thousand Nights and reads a list of children in Japan they are using.

Guren and Shinya play Bomberman while elbowing each other. It is now 3:30 a.m., and Mito and Goshi have both fallen asleep. Everyone starts waking up, so Sayuri offers to make them supper.

Another day, Guren visits Shinoa's apartment, which is large enough for a couple or a small family. He finds her sitting in the dark with a blank expression. He notices there is no refrigerator, and the only things present in the kitchen are canned foods and a microwave. Guren invites her to his house for dinner and says he has good cooks, but Shinoa does not trust him so easily. She says Mahiru told her Guren betrayed the Imperial Moon, and his father is being held hostage until his execution. Kureto sends Guren a message to keep an eye on Shinoa in case Mahiru contacts her.

Shinoa calmly throws a knife at Guren with an exploding tag on it, but he easily catches the blade between his fingers and tears off the talisman with his thumb. Shinoa comments that he is strong. She says Mahiru told her they had sex and teases Guren about it.

Sayuri calls Guren after they undergo more experimentation under the Imperial Demons. Guren orders them to prepare a good meal for 7:30 p.m. and says he is bringing a guest.

Shinoa's phone begins going off, and she insists the only people who call her are Mahiru, solicitors, and people with the wrong number. Guren eventually answers it.

Mahiru chats with him while Kureto sends Guren messages on his own phone. He struggles to not warn her about Kureto coming after her. She eventually hangs up, stating that Kureto has arrived and is about to start the party.

Guren takes Shinoa with him, and she points out his is only doing this out of guilt.

Guren steps out of the apartment with Shinoa at 6:15 p.m. They take a taxi, and the driver complains about being his previous job letting him go and how his two passengers are so fortunate to be born into wealthy families. He complains about the cozy life he believes Guren and Shinoa lead, which makes Guren laugh and makes Shinoa say he is being too talkative. They go onto the Metropolitan Expressway.

They hear a screeching sound, and Shinoa jumps out of the car while Guren drags the driver out with him. A dump truck falls onto the taxi and then falls onto a mother and child. Guren summons Noya and cuts the truck in half to save them.

The civilians begin screaming. Guren orders Shinoa to return home and gives her 10,000 yen for a taxi. He tells her to get a meal before going back. He says he will stay to observe the situation awhile longer. They tell each other to be careful and then split up.

Guren finds Mahiru surrounded by four vampires in human clothing in the midst of a large-car pileup. She is protecting an orphan named Juni with Asuramaru and has curses encircling her skin. She appears panicked. The four vampires defeat her and drink her blood until she faints. Although Guren wants to help her, Mahiru tells him not to and mentions the vampire queen of Kyoto before a vampire steps between them.

A vampire approaches Guren and tells him not to block the way. Guren does not interfere since they cannot defeat a vampire even with Noya. A helicopter collects Mahiru, Juni, and the vampires.

Guren looks at Asuramaru on the ground, and Noya tells him not to touch other demons. Asuramaru soon dissipates into the air.

Police sirens sound, and Kureto calls Guren. Guren reports being at the scene but says it was over when he arrived. He notices that all of the CCTVs have been destroyed and the witnesses killed. He suspects Mahiru did that on purpose. Guren says he is going home for dinner. He leaves, and Imperial Demon soldiers disguised as police officers let him through.

It is the night before September 29th. Shigure approaches Guren and asks to know what is bothering him. He decides to reveal his father's situation to Sayuri and Shigure. Sakae calls him and apologizes for being weak until Guren begins shouting at Kureto, and Kureto ends the call. Guren throws his phone at the TV and cracks the TV screen. Guren tells Sayuri and Shigure that he has to kill Mahiru within forty-eight hours or else his father will be executed.

Mito, Goshi, and Shinya visit. They heard Guren's yelling. Shinya warns Guren that he cannot save Mahiru. They discuss how they can kill Mahiru. Guren shows his friends the documents he took from Mahiru's apartment. They list the children involved in the Seraph of the End experiment and prophesize the destruction of the world. Guren says Mahiru was taken by vampires on the Metropolitan Expressway and mentioned the vampire queen in Kyoto. Shinya asks if vampires have a monarchy since they have very little information on vampires.

Shinya tells Guren he shared that information too late.

Guren recalls Mikaela Shindō and Saitō in the Shibuya branch of the Hyakuya Orphanage. Guren mentions them and says that Mahiru told him not to get close to the orphanage. He wonders if Saito betrayed the Thousand Nights to work with Mahiru. He recalls Yūichirō Amane. The group is aware they are being completely manipulated by Mahiru.

Kureto visits Guren and orders him to kill Mahiru within forty-eight hours or else he will kill Guren’s father and the rest of the Imperial Moon. He calls Aoi, stating that Guren betrayed them and cut him down. He orders Sakae’s death, but this is all a ruse.

Guren and his group escape to the roof and steal Kureto’s helicopter before heading to Kyoto. They crash in the mountains in Kyoto. It takes them a few hours to descend.

The boys have a peeing contest. Although Guren mocks them for it, he's the most enthusiastic.

They pull out a map and compass and plan to buy civilian clothes more suitable to their situation than skirts and court shoes. They plan on taking the shortest route since they figure the supposed vampire settlement will prevent the Imperial Demons and the Thousand Night from hunting them down so easily in their territory.

When planning their battle formation, Mito scolds Guren about not listening in class, but he quickly corrects her by saying he already mastered all of the academic courses set by the Hiragi House and had no need to listen. He decides on a Tenka Battle Formation, which is also known as the Moon Demon Company. He is concerned that they have little experience using cursed gear in battle. He adjusts the formation to have Guren and Shinya as the vanguards with Goshi and the girls as four rearguards.

They group comes across a truck, and they discover that each of them has been trained to hot-wire vehicles. Goshi starts up the car immediately, impressing Mito with his skill. Guren and Shinya notice that the owner left the key in the ignition, but Mito does not notice and keeps praising Goshi's skill. Guren naps while the others keep a lookout since they say it is impossible to sleep in the loud and shaking truck.

Guren faces Noya. Noya's voice is fuzzy thanks to Kureto's demon-suppressing talismans, but he still tries to tempt Guren with power. They chat, and Noya reveals that demons are born from passionate desires. As such, they appear in the forms when they were most innocent and pure, when they felt like everything was possible. Guren says this is around twelve.

Noya tempts Guren with power, desire, and knowledge. He says he was first a human, then a vampire, and now a demon. If Guren takes his hand, he promises to give Guren Mahiru's secrets. Guren recalls the fun times he had with his friends and resists Noya's temptation. When Guren refuses, Noya threatens to give Guren what Mahiru left to him.

Guren wakes up on the truck with Shinya watching over him. He slept for seven hours, but no one wanted to wake him because he was talking with his demon. Goshi and Shinya have been taking shifts looking after him.

They enter the love hotel where the others are resting, and a pair of students in sailor uniforms mistake Guren and Shinya for a couple. They find Goshi listening to porn while sleeping. Before Guren turns it off, Mito rushes in and scolds them for their impurity. Goshi wakes up, and the other girls arrive. Guren puts on the news and changes into civilian clothes.

Suddenly, Asuramaru drops down in front of him, but Shinya quickly knocks it away before Guren comes into contact with it. Asuramaru unsheathes, screeching loudly as it lodges itself into the ceiling. Guren tells his friends that this is Mahiru's sword and says he did not realize he had it.

A vampire breaks in through the window and tells them not to move. Guren summons Noya and performs a more powerful attack than he has ever performed before. She catches his sword in her mouth.

Guren orders the squad to use a retreating formation with him as the sacrifice instead, but Shigure and Sayuri attack the vampire instead of retreating. The vampire catches their weapons and comments that they are quick. They struggle against her, and Guren meets with Noya. He orders Noya to become his friend, which makes him blush from such overt craving. In exchange for feeding Noya with desire, Noya agrees to give Guren power.

Even so, this power is not enough against a vampire.

Mito appears in front of Guren and is stabbed in the chest. She coughs up blood from a fatal wound. Looking back at him, an expressionless Mito tells Guren they're using the Tenka Formation. Guren realizes this is not Mito but rather one of Goshi's illusions.

Using the illusions, Guren cuts the vampire in the neck. The vampire is unable to defend herself in time because Shigure placed talismans on her sword and detonated them. Shinya appears from behind, cutting off her sword arm, and Mito sends the arm flying into the hallway. They continue fighting, and the vampire wonders why her wound will not heal. She turns to escape through the window but is stopped by an illusion of a wall. While she is distracted, Shinya cuts off her feet. Guren stabs her through the chest.

The vampire expresses fear for the first time. Guren announces that they are finally a step ahead of Mahiru and says they will get information from this vampire.

On October 2nd, Guren has a final meeting with Sakae before his execution. Sakae appears to have aged, but he denies being interrogated. Guren tells Sakae that Sakae did not drag him down, and Sakae tells Guren that it is not his fault that Sakae will be executed. Sakae pats Guren on the head and tousles his hair. Guren begins crying.

Since Guren captured a vampire and acquired Asuramaru, which would be highly useful for their research, Kureto initially adjourned the execution date of Sakae and the Ichinose's subordinates. However, Tenri Hīragi and the heads of the other nine houses overturned this decision. They wanted to prevent the Ichinose house from gaining to much power. Sakae tries to have them part with a smile.

Sakae smiles, and Guren asks why he is always smiling. He says he is always happy, but Guren calls him a liar. Sakae claims that Guren will live on and become the head. He says no one will protest this, and that makes him happy.

Sakae tells Guren to continue doing what he feels is right.

Soldiers intrude and tell them it is time to execute Sakae. He hugs Guren tightly and tells him farewell. The troops shackle him and take him out of the prison. As Guren watches him leave, he shouts that he was happy being born as Sakae's child.

Eventually, Kureto approaches Guren and tells him the execution is over. He says he opposed the execution, but his father made the final decision. Kureto reminds Guren that he is Kureto's subordinate and does not belong to Tenri Hīragi.

Guren approaches the execution grounds and notices cameras before finding his father's decapitated corpse. Guren ignores Noya's temptation. He answers a phone call from Shinya, who tells him they will clean up the scene. Guren tells him there is no need and asks them to come play a game with him later.

Standing straight, Guren walks into the grounds and hides his emotions. He then cradle's Sakae's head and then carries it with the body using Noya's strength. The onlookers watch silently.

And thus, Guren becomes the head of the Ichinose family.

Sakae’s body is returned to Aichi, and his head is reattached prior to his burial. Guren dresses in his father’s ceremonial kimono and greets the other family heads.

Shinya, Goshi, and Mito sneak in to visit him. In an attempt to cheer Guren up, Goshi brings Guren a porn mag and even manages to convince Mito that it is okay. Guren ignores him. When Guren asks if their houses allowed them to come, the Mito and Goshi side-step the question but say they are on holiday.

Shinya brings a brand-new game over to Guren.

They play games until 2 a.m., and Mito manages to trump everyone in the wrestling game. After playing so late, they fall asleep and all rest in the same room.

Noya chats inside Guren's heart, mentioning the demon already there and Guren's desire to not lose and to gain everything possible. He says he likes Guren the best and will be very happy if he becomes a demon. He says he must thank Mahiru.

Guren wakes up and steps outside under the moon, overwhelmed with a desire for revenge.

The funeral continues for two more days, and Makoto Narumi and Shūsaku Iwasaki whose families serve the Ichinose in Nagoya, ask Guren if the Imperial Moon will be treated like this for the rest of their lives, and he tells them to endure it and support him for now. Shigure and Sayuri's fathers are relieved that Guren has not changed after living in Shibuya.

Guren leaves with Shinya, Mito, Goshi, Shigure, and Sayuri to return to Tokyo and attend a meeting of the higher-ups. Mito brings cards for poker.

Guren reports to the Hīragi headquarters but he is forced to wait an hour before being summoned. Tenri Hīragi orders Guren to kneel before him and says he forced Sakae to dance naked. Tenri brings up how Guren deceived Seishirō in Book 1 but says it is Seishirō's fault for being deceived. Tenri scolds Guren for the look in his eyes and forces him to kneel before him while he stomps on Guren’s head enough to make it bleed. He eventually acknowledges him as the head of the Ichinose house and tells him to put in his best effort to maintain his subservient existence. The other heads laugh at him. Guren realizes Mahiru grew up in a place like this. He dismisses Guren.

Guren leaves, and Kureto is waiting outside for him. He joins up with Guren and asks him what happened and gives him a handkerchief to wipe away the blood. Guren ignores him. When Kureto offers to take him back to his apartment, Guren asks him what kind of strange wind is blowing today.

Guren wonders if Kureto despised his birth like Mahiru. He walks home on his own.

Shigure and Sayuri panic at the blood

Guren then walks in on Saitō lounging on his sofa. Then Guren moves to attack him, Saitō brings Guren's aides to his attention. Sayuri and Shigure are bound in chains and unconscious in the corridor. Despite Saitō's threats, Guren cuts the chains on them and summons Noya. Saitō attacks him with chains, and they fight.

Guren tries to figure out who Saitō is. Saitō says he is an assassin from the Thousand Nights and says he betrayed them. Guren asks about Mikaela Shindō and Yūichirō Amane, which changes Saitō's expression.

Guren recalls Mahiru's notes and prophecy. Saitō reveals that Seraph of the End is not a bioweapon but is actually punishment from the gods. Saitō says the arrogant and idiotic humans want to weaponize it and not use it in better ways. Saitō admits he has a better way of using it and invites Guren to join him and Mahiru.

Guren wonders what he has to sacrifice in order to become strong.

Curse marks appear on Guren's skin as he maximizes Noya's strength and requests that Saitō bring out his cursed gear as well. Saitō says he actually came empty-handed and says he could defeat Guren with his bare hands. Guren keeps attacking him but cannot hit Saitō at all. Saitō's movements are on a completely different level from when they fought before. Eventually, Saitō tricks Guren into cutting off Shigure's left arm.

Guren is on the verge of losing control, and Saitō presents both Sayuri and Shigure as meat shields.

Guren compares Saitō's ability's to Ferid's. Saitō says he is a human, but then contact lenses fall from his eyes and reveal red irises. He also has fangs. When Guren asks if he is a vampire, Saitō denies it and says he was a human thousands of years ago. For the third time, he requests Guren to join him. Saitō reveals he was a second progenitor hundreds of years ago.

Saitō teases him a little and then warns him that he will regret not moving forward today. He says Guren greedily craves everything, so he will lose many things. When Guren asks if Saitō made Mahiru go mad, he says that she was crazy from the start. He says Mahiru only wants Guren and lives to build a future with him.

Guren puts Shigure's arm back at the cut and carries her to her pink room. He places her on the bed and puts the cursed gear weapon Shigure is contracted to on her chest to advance her healing. Guren tries to wake her up but is worried she will die from blood loss before the arm will completely reattach.

Guren calls Kureto, who orders Guren to take her to the lab. He sends a helicopter.

When Shinya calls, Guren says Shigure accidentally cut off her arm while attempting to chop up a radish. When Sayuri calls, Guren orders her to clean up the room coated in Shigure's blood.

Guren informs Kureto about Saitō. Kureto says he will investigate Saitō, and he reveals they have learned quite a bit of information thanks to Asuramaru. They successfully reattach Shigure's arm.

When Guren heads home, Seishirō attacks him with a group of ten soldiers, but Guren is simply relieved it is not a vampire. Seishirō orders Guren to kneel down, but Guren refuses. Seishirō picks a fight, and Guren finishes it. Shinya prevents Guren from landing the final blow. Shinya convinces Seishirō to leave Guren alone.

The usual group meets at Guren's apartment, sans Shigure, who is still being treated. Guren tells them what happened. Then, they eat curry and play more games. Mito owns them at Bomberman once again, and Guren marvels that she has surpassed the skills of a human.

On December 10th, the high school students are using demons, and one goes berserk. Kureto sends Guren, Shinya, Goshi, Mito, Sayuri, and Shigure in to kill him, and Guren is the first to arrive. He comes across a classroom with twenty-seven corpses, and a girl missing an arm and leg comes out, chased by a boy with black eyes and curse markings all over his skin. Guren knocks him out instead of killing him.

Mahiru appears, applauding Guren's strength. She admits this is her doing and does not care about the victims. She asks about the experimentation on Asuramaru. Humans must undergo surgery in order to meet qualifications to use a Black Demon, but the current success rate is less than 20%. Most people die. Although Kureto, Shinya, and Guren had successful surgeries, Goshi, Mito, Sayuri, and Shigure did not even meet the basic criteria to have the surgery done.

Guren says he wants to protect both her and his friends. He asks her to surrender, so they can extract the demon from her. Guren has Noya possess him, and they fight. He now knows the strength of the demons and believes he can defeat Mahiru, but he has yet to realize she is now a vampire. The rest of the group arrives and fights her. Mahiru feigns surrender before passing Shikama Dōji to Guren. She instructs him to give it to Shinoa to protect her after the Apocalypse begins.

Guren notices a weak, red light gleaming in Mahiru's eyes too late. She beats him down and drinks his blood. After telling Guren she loves him, she leaves.

On December 11th, Mito confesses her feelings to Guren, but he rejects her and they remain companions.

On December 23rd, Guren investigates the abandoned Hyakuya Orphanage in Shibuya, where Mikaela Shindō is supposed to reside. Although the reports say the children have been killed, it shows signs of recent habitation. He finds Mikaela's diary. Mika has shockingly nice handwriting for a child. The diary is last dated for December 8th and mentions moving to a new place. Guren reports this to Kureto, and Kureto says the information came from the Nii and Kuki family families, meaning they have become traitors.

At 1 p.m., Guren takes Shikama Dōji to meet with Shinoa. The traitorous faction attacks them, but Guren kills them quickly and incidentally drenches Shinoa in their blood. Shinoa loses consciousness as soon as she touches Shikama Dōji, but Guren manages to escape with her.

Goshi calls Guren and reports that Guren's apartment was set on fire by the traitors. Their phone call is interrupted. Guren steals a motorcycle and escapes, but a van chases and crashes into him. Traitorous soldiers face him, but Shinya attacks with Byakkomaru while pulling up on another motorcycle. Goshi arrives in a stolen minivan with the rest of their squad and picks them up. He says policemen are still chasing them. They ask Guren what they should do about the end of the world.

Guren calls Mahiru and says he will betray the Hīragis and join her. She laughs.

Prologue
Guren arrived outside the entrance of Sanguinem during the daytime after Yu's escape from the vampires. He says that one of the lab rats from the Hyakuya laboratories, the company responsible for destroying Japan, is there just like the prophecy said. He tells Yu that he will be useful in exterminating vampires. Exactly what prophecy he refers to has yet to be mentioned again in the series.

Second Shibuya High School Arc
Over the next four years, Guren trains Yu to become a soldier of the Japanese Imperial Army. He teaches him how to survive above ground, how to live in the Demon Army's cities, and how to use a sword. Unfortunately, he is less successful at teaching Yu obedience and subordination, which is shown in 2020 in Shibuya, Tokyo. At some point Guren was sparring with Yu and stated that kids like him are weak and questioned whether Yu really thought he was going to get revenge on vampires like that. Guren told Yu that he could not handle it before joking how Yu was crying. He was pleased with Yu's resolve to become stronger. Once Yu is sentenced to high school for his disobedience, Guren assigns Shinoa Hīragi to act as Yu's surveillance officer. When Yu refuses to follow orders to make friends, Shinoa gives him a note with the written orders. This note is the first time anyone in the series addresses Yu as a "virgin." Although Shinoa mocks him for being a virgin most often, Guren may have given her the idea to do so in the first place.

During those four years, he also worked on human experimentation for the development of Black Demon Series bearers. Shinoa finds Guren during alerting him that a vampire escaped onto the school grounds. Guren kills the vampire attacking Yu, giving her an unpleasant surprise when she realizes he used a cursed blade. Again Guren rejects Yu's request to join the Moon Demon Company to exterminate vampires. Yoichi appears, tackling Yu and appearing as his friend. Guren makes good on his promise, finally accepting Yu to the Moon Demon Company along with Yoichi.

Shinoa informs Guren when Yu manages to overcome a myo-o demon's thrall on his own. After that, Yu and Yoichi attend their first class class in the Moon Demon Company barracks. After he introduces them, Yu picks a fight with Guren, and Guren assigns Yu the seat in front of Kimizuki. Naturally, the two boys start another fight, and Guren finishes it.

Later on, Kimizuki arrives in Guren's office and asks him if he can receive a demon weapon since he is stronger than Yu, but Guren turns him down, warning him that he will be devoured by the demon if he has no bonds to pull him free from the demon's clutches. Some time later, Shinoa recommends both Yu and Kimizuki to Guren as candidates for the Black Demon Series weaponry. He plans to rebel against the main family.

Following that, he's seen rebelling by sleeping and snoring during a meeting with the higher-ups. He manages to escape a "stupid" political meeting by appearing rude. Yu attacks him, and he decides to proceed with Yu's training so that the upper brass do not notice him. He kicks Yu in the head before continuing with his day.

Guren ultimately appears in the training classroom. Sayuri informs him that Yoichi may be stable enough to resist demonic temptation. Guren attacks the classroom, filling with Mahiru-no-yo demonic aura that sends most of the class tumbling to the floor, many of whom go unconscious. Sayuri struggles to stand by using two spell tags. Yu and Kimizuki tremble. Shinoa manages to remain standing just fine, and Yoichi is completely unaffected by the attack to the point where he does not even feel it. They are the only ones standing. Since he experimented on the three boys previously for this purpose, he is not surprised when they stay standing. Contrary to his expectations, Shinoa remains standing as well, proving herself as a possible candidate for Black Demon Series Cursed Gear as well, much to Guren's chagrin.

Before he takes the three boys to make contracts with demons, Sayuri informs Guren that Yoichi may not be strong enough to accept the demon, although his heart is very stable. Guren takes him anyway.

Yoichi becomes possessed, and Guren orders Yu and Kimizuki to kill him. In the end, they manage to help Yoichi regain control and turn back to normal from being a man-eating demon, and it is actually Guren's words that make him snap out of it. Shinoa wonders if Guren planned this ending from the start.

Shinjuku Arc
When Guren assigns Mitsuba Sangū as the fifth member of Shinoa's squad, she protests against being assigned to a squad of rookies, especially working under Shinoa. Eventually, she submits. Guren and his team enter the field early on in the battle at Shinjuku. He scouts for the enemy commander, spying Mika and Ferid. Ferid spies him back which Guren finds mildly concerning. Then, he charges in at the 5th Street intersection, killing several vampires with a single strike. He leads the battle, facing off against Mika.

At the Shinjuku 5th Street intersection, Guren and Mika fight head-to-head. Although Guren complements Mika's strength which Mika responds by saying Guren is not very strong. Guren uses a fudo myo-o spell to cause on explosion. Mika dodges easily, but Ferid warns Mika his arrogance will be his downfall and offers his assistance once more. He points out that Guren never planned to fight Mika one-on-one. Shigure set a trap, but Mika manages to escape. With the help of Goshi's illusion, Guren attacks Mika from behind, claiming checkmate; however, Ferid steps between them and blocks the attack. He backhands Guren and sends him flying. Mika lets Guren talk for a few seconds with his team, and Guren decides to take a second potentially lethal pill. However, Mika attacks him before Guren can ingest the medication. When Guren asks if Mika has gotten faster than before, Mika claims he stopped holding back. Guren calls him a naive brat. Mika defeats Guren and stabs him through the chest. When he attempts to kill Mika with Yu's help, Yu freezes, and Mika escapes. Enraged over Guren, Yu arrives. Mika recognizes him and turns around, but Yu pierces Mika through the chest with Asuramaru, calling him a bloodsucker and telling him to die. Then, he recognizes his not-quite-dead best friend and family member. Guren grasps Mika's sword with a spell tag and urges Yu to activate his weapon and kill the vampire, but Yu freezes when he realizes who he just stabbed. Mika releases his sword and escapes. Guren hits Yu and asks him why he did not kill that vampire when he had the chance.

Although Yu desperately wants to reclaim Mika, Guren issues orders to retreat. Ferid plays with Guren, eventually grabbing him by the neck. Ferid swindles his opportunity to kill Guren, and he asks him about Yu, even though Ferid already knows the answers. Guren calls Yu's transformation his "ace in the hole" after subduing the it by commanding Shinoa to embrace Yu. Guren makes a comment about being a decoy, and Ferid notices Shinya, barely escaping a sniping attack. The main forces arrive, chasing away the vampires.

Across the field, Shinoa tells Guren she has questions for him, but he says he will not answer them.

Post-Shinjuku Arc
Shinoa spends five days hunting him down before finding him in a lab underground. She tells him that Yu has not woken up since his transformation. Shinoa asks him what she did to Yu, and she reveals that she gave Yu different supplements than the other members of her squad. Guren refuses to give any direct answers. He states that Shinoa's sister, Mahiru, invented Cursed Gear, and that sacrifices are necessary before scolding her for her idealism. Guren then asks her if she has a crush on Yu, and states that he does not care. He orders Shinoa to leave as well as informing her that the drugs wear off after five days, so Yu should wake up soon.

Guren waits for Yu while Yu heads to meet with the higher ups. Guren asks him if he is wagging his tail for the main family like a good mutt. he realizes Guren does not get along with the upper brass. Guren reminds Yu that he saved Yu, taught Yu how to live here, and taught him how to use a sword. He tells Yu that he is alive because of him. Yu is his and belongs to his faction. So Yu shouldn't go wagging his mutt tail to the Hīragi.

Yu tells him does not care about his stupid politics and says he will never abandon or betray his friends ever again, so Guren should quit worrying. Guren says that he is not Yu's friend but rather his superior, savior, surrogate father, and adding all those things up, practically a god to him. Guren says Yu can call him "papa," but Yu declines.

While Yu attends his meeting, Guren meets with the demon Mahiru within his mind. When Yu exits with an injured Yoichi and Kimizuki, he yells at Guren to teach him the proper way to use his Cursed Gear.

Guren meets with Shinoa and Yu before the actual squad meeting. As he saw them holding hands, he sarcastically asks if their gonna skip off to make out. Yu counters by saying that Guren is late. Yawning, he tells Yu to shut up as he was up all night in stupid army meetings. He tells Yu that he's tired and in a foul mood and asks if he can go home and Yu promptly tells him no. He claims that both Mitsuba and Shinoa can teach them how to use their weapons properly. Shinoa manifests Shikama Doji and explains that manifested demons can use special abilities. Yu asks Guren if he could do that with Asuramaru. Guren tells him that it depends on the type of demon he is. There are some like Shinoa's and then there's the type of demon that directly possesses the user to grant immense physical strength. He says his blade is the latter.

Guren challenges Yu to a fight to see if he's ready for the next step. He tells Yu to draw and activate his sword and he'll only do a normal activation. Yu is excited, stating that's it's been a long time since their last spar. They spar and Yu asks him if he's gonna compliment him on his skills as he says that the gap between them isn't as big as before. Guren says that it's only due to using only standard activation. He says next he'll have his demon possess him. He orders Mahiru to possess him. He tells Yu that if he can take one hit then he'll get his compliment. He then promptly flings Yu from the rooftop. After hearing Guren summon his demon by calling out her name, Shinoa holds her scythe at Guren's neck. She reveals that her weapon specializes in long-range combat and consequently stands no chance against a melee fighter like Guren at that range. Guren calmly says he would let Shinoa kill him. Shinoa asks him if that is his way to atone for killing her sister, unbeknownst to her that Mahiru stabbed herself by Guren previous demon. She asks if she is in his sword since she heard him call her name. Guren says that Mahiru is already gone since she turned into a demon and saved the world by completing Cursed Gear. Shinoa laughs, stating that Mahiru was never one to care about the world because she loved him. She longed to be with him since they could never be together and became obsessed with demons.

After discussing the events of eight year, Shinoa says that if Mahiru hadn't completed the development of Cursed Gear, humanity would have perished. Her sister, who was just a girl in love became something like a Messiah. But then she was killed when she became obsessed with her research and became a demon. She continues saying, the one who killed Mahiru was the person who used to be her lover, him, Guren.

Shinoa asks him if Mahiru is together with him inside his sword, stating that he is being possessed by her. Guren asks her if she and Mahiru ever got along. She explains that she was not close with her sister because Hīragi's are raised without knowing familial love. He tells her to shut up and drop it.

Shinoa then tells him that watching a "certain someone" get so desperate to save someone he has no blood ties to has made her wonder if she should put more value into "friendship" and "camaraderie". From that she asks if making use of Yu was one of Mahiru's orders and asks if her sister or the demon for lack of a better word that is inside his sword is ordering him. She asks what his goal is, though he doesn't say anything. As if warning him, she asks that if his goal is something that does not benefit Yu, that she'd appreciate if he stopped. Guren sighs and asks if she seriously is head over heels for him.

Yu slams open the door, yelling that he's back and tells them that he tried climbing up the building with his sword. He wants Guren to teach him how he did that with his demon. As Yu and Shinoa chat. Guren sheathes his sword and thinks that

The rest of the squad arrives half an hour early, interrupting their meeting.

Guren tells her that Mahiru is dead and isn't coming back. He says that the demon inside his sword is under control so he isn't being possessed by her. But Shinoa doesn't believe him. He orders Mitsuba and Shinoa to advance the training of the three new recruits before heading elsewhere for a nap. Before he leaves, Yu asks if he and Mika were really guinea pigs used by the Hyakuya sect for human experimentation. He asks if Guren rescued him in order to use him. Guren answers that he has no time or resources to rescue those he cannot use. He asks if Yu is mad at him but Yu tells him that whatever his reasons, he would have died if Guren hadn't rescued him; he feels that he owes him. Yu wants to know if he himself is useful to him. He doesn't care about the fight between Guren and Kureto is, all he wants to know is if Guren needs him. If he does, would he want Mika as well and if so, he will be Guren's guinea pig or anything he wants. He'll do whatever he can to help him; all he wants is to get Mika back. Guren says that everyone standing there is family, including him. Family works together to bring family back. He finally leaves to go home and sleep.

Nagoya Arc
Guren is seen meeting with Kureto Hīragi. He walks up toward where Kureto oversees five chained and starving vampires. Kureto claims he is testing to see if he can force vampires into becoming demons, so they can create Cursed Gear more efficiently. He claims that most of the low-level vampires do not turn, and those that do turn become weapons even weaker than the replicas of the stronger weapons. Kureto orders them killed and steps down to speak with Guren. They bicker a little, and Kureto asks Guren how he created so many Cursed Gear users (Yu, Yoichi, and Kimizuki). Guren starts saying that he just got lucky, but Kureto says that every single human capable of bearing a Black Demon has been a human experiment at one point. Even with the experimentation, the chance a candidate is successful is slim. The fact that Guren managed to create three of them, all successful, is extremely impressive. Instead of pressing the issue, Kureto tells him that success is a boon and asks that he share his experiments with them if more are successful. Kureto then asks Guren if he is planning a coup. They reminisce briefly on their high school days. Kureto calls Guren out on what he sees as his weak point: no matter what happens, he claims that Guren cannot betray his friends. He says this weakness is why Guren is unworthy of being a leader and also why he trusts Guren. Guren asks him what hostage Kureto prepared this time, but Kureto says he was too busy. Kureto asks Guren about his vision. Kureto announces his dream of eradicating all vampires in Japan, then crushing all other surviving human organizations, and finally uniting the world under the Japanese Imperial Demon Army.

Kureto then gives him orders to lead a pre-emptive strike with 100 soldiers on the vampires in Nagoya. Guren calls it out on being a suicide mission, but Kureto claims it is a vital mission instead. After Kureto leaves Mahiru manifests and tells him to only obey her, but Guren tells her to go away.

Proceeding with the mission, Guren waits for his troops to arrive at the Ebina rest stop prior to leading the strike on Nagoya. While his squad messes around, Shinya arrives unannounced to give Guren a hand. He also believes this is a suicide mission. He gives a brief speech to his squad, causing Sayuri, Shigure, and Mito to blush. When Goshi and Shinya tease him for giving the speech on a sports car, he manages to hit Goshi and orders Sayuri and Shigure to get him a different stage. When Shinoa's squad arrives late, he scolds them vehemently. Yu takes the blame, and Guren promises to punish him later, even though he knows Yu is covering for Shinoa.

Guren gives a speech to the Moon Demon Company, and Shigure hands out orders for the individual squads.

At the Ebina rest stop, he summons Yu for his punishment. They chat, and Guren tells him he is glad about Yu's attitude change. Yu also chats with the rest of Guren's squad, finally realizing that Sayuri is his teacher. He recognizes Shinya as well. Moving on, Guren orders Goshi to create a mortifying illusion of a naked Yu screaming for his mommy. Hearing his screaming, the rest of Shinoa's squad charges in, and she breaks the illusion.

After scolding her, he challenges her to a match: Guren, Mito, and Shinya against her entire squad. He gives her ten seconds to prepare.

Guren strikes off against Yu, quickly distracting him with an explosion ward and getting past him to strike Mitsuba and Shinoa. He lectures him. This exercise teaches Shinoa's squad a lesson, helps Shinoa's squad gain focus, shows off the strength of the newbies as three wielders of the Black Demon Series, and raises moral of the troops.

Beginning their mission in Nagoya, Guren's squad charges underground, eliminating vampires as they go. He assigns three squads to each of the eight nobles they are targeting. Shinoa and Narumi's squad are the only group to have only two squads, and he leaves Shinya with them to take over command if something happens to Guren. Guren's squad takes on Nineteenth Progenitor Mel Stefano on their own. Although they succeed, Guren and his squad are pretty bruised and battered. His squad claims he nearly died eight times in that fight, and they decide to use at least two squads in their next attack.

A soldier named Kusunoki reaches Guren, collapsing to the ground and giving him information. He says ten soldiers were killed and another twenty are hostage in Nagoya City Hall. This means that six squads were exterminated while hunting their two vampire targets. Even though this is an obvious trap, Guren's squad goes to reinforce Shinoa and Narumi's squad. He adds a new target to their list: Thirteenth Progenitor Crowley Eusford.

When the Moon Demon Company regroups, he asks Narumi for a report on rookies' teamwork, and Narumi tells them they did very well. Sergeant Aiko Aihara reports that she lost 8/15 of her team, and Guren tells her that is not her fault. Guren orders Narumi Squad and Shinoa Squad to accompany him in exterminating Thirteenth Progenitor Crowley Eusford, Seventeenth Progenitor Chess Belle, and Seventeenth Progenitor Horn Skuld and rescuing their comrades. Shinya asks him if he is okay after losing so many people today, and Guren says he will just cry later. He informs the squads they will only attack for ten minutes. He orders Aiko to wait half an hour for other squads and to send them to Nagoya Airport.

Once they reach Nagoya City Hall, Guren looks at the hostages being used through a telescope and knows that they are being used as bait to lure them. Yu insists on bursting in and saving them. Narumi dismisses it as too dangerous and when Yu asks him what they should do, Narumi asks Guren what they should do. Guren suggests that they snipe them from their position and see if they can lure them out but says that if there are too many of them, they are to abandon the hostages and run. Yu shouts that they can't do that.

Shinoa interrupts Yu and asks Guren what their priorities are. In order, he says that their top priority is to maintain their numbers, letting no one die. Their second priority is to free the hostages and lastly, getting the hostages out alive. Narumi states that this is because they are needed for another mission after this. Guren then says that they need to keep the vampires occupied in Aichi Prefecture for as long as they can so they can buy enough time for the main forces in Shibuya to get prepared.

He says that once the hostages are free, they need to draw as much attention to themselves as they can and then begin their next mission which is to survive as long as possible. Shinya says that essentially, the plan to actually make alot of commotion only to run away in the end. Guren says that's right and if it goes well, the squads that are finished with their assassination mission will hear the commotion and find them and then they'll kill the vampires holed up in city hall.

After Crowley catches Gekkōin, Guren and his squad discuss what to do while Crowley, Horn Skuld, and the Seventeenth Progenitor Chess Belle wait patiently for them. After careful planning, Guren decides that his squad will take his squad to attack Crowley while Shinoa and Narumi Squads free the hostages. He gives them five minutes to rescue as many hostages as they can and act as a proper diversion for the main force in Shinjuku. As soon as the five minutes are up everyone has orders to retreat to the Nagoya Airport immediately.

Guren and Shinya attack Crowley at the same time but he easily negates their attacks at close range. He then swings Guren into Shinya, throwing them into the wall behind them. Crowley, Chess, and Horn then step toward them. Mito notices this and moves to assist them but Goshi holds her back and tells her, she would only get in the way.

Sometime later, Yoichi reports on this situation with Guren's squad to his squad and Yu insists on rescuing him. Shinoa agrees with him but says they only have five minutes. She gives them specific instructions regarding their plan. When Shinya and Guren attempt to flee from Crowlely, Chess, and Horn, Shinoa Squad breaks through the floor below, and Yu attacks Crowley. The vampires easily block and counter the humans' attacks.

Guren orders them to escape, and Shinya agrees. Shinoa orders Yu to leave as well. Guren calls Goshi out of hiding, and Guren's personal squad breaks in through the windows. Goshi creates an illusion, allowing the humans to escape, but they are forced to leave Guren behind.

Crowley orders Chess and Horn to restrain Guren and take him with him.

In Yu's flashback, Guren comes to check up on him. Yu cries in his bed. Guren asks about what dream Yu had, and Yu says its the same one he always has: Ferid Bathory slaughtering his family. Guren asks if this means he wet the bed again, and Yu snaps, stating that he never wet the bed. Guren says he will stay there until Yu falls asleep. He sits by Yu's bed and reads documents on the Seraph of the End project begun by the Hyakuya Sect. He stays there from 2:20 a.m. until 2:50 a.m. Yu says he has never really had a family since he was born because his parents called him demon spawn and tried to kill him. He says he made a new family, which was killed anyway. He says that living is painful and wants to know if it is even worth it.

Guren states that living hurts him, too. He says he failed to save the one he loved most, but, if he sticks around, then a day may come where someone needs him. He instructs Yu to live until he finds a new reason for life and people who need him. He leaves Yu and orders him to sleep. After Yu rushes off and challenges Crowley, Guren, whose wrists have been bound, gets between Yu and Crowley and orders Yu to leave because Crowley is more powerful than any other vampire he’s fought. When Yu asks why he is still not strong enough, Crowley answers that it is because Yu is only livestock and asks if Yu fears cows and pigs revolting someday. He insists vampires will never fear humans. Yu repeatedly yells at him to shut up and die, and they exchange blows. Guren orders Yu to stop. He says that Yu's demon will take over if he uses more power than that. He calls Yu a stupid brat as he told him that he’s already done for and Yu should abandon him and run. Yu yells at him not to not dare give up as Guren was the one who told him to live despite all the pain. Yu tells him to be a good adult and be a good example for him.

Crowley mutters that he is beginning to get bored and even though Yu is a key part of some silly little human plot, he’ll kill him. Yu tells him that he’ll never give up. Guren tells Yu that he has a plan, but Yu needs to leave. Yu does not listens and demands even more power from Asuramaru. Guren tries to stop him, telling him not to let his desires swallow him. Yu's desires overwhelm him, and half of his face darkens and a horn sprouts from his head as he becomes a demon.

Yu challenges Crowley again. Kimizuki appears behind him, telling Kiseki-Ō to begin the count to nine until the devil's coffin opens. After Kiseki-Ō gets to four, Yu invites Kimizuki to kill this bloodsucker together, but Kimizuki notices Yu's horn. Guren warns Kimizuki that Yu has been possessed and he’s lost all control of himself. He tells Kimizuki to grab him and run. Yu tells Guren to shut up now that he has the power to rescue him. Kiseki-Ō finishes the countdown and captures Yu with the devil's coffin.

Guren shouts that his final order to them is to live and escape.

The captured Guren is next seen on his knees, with his wrists in cuffs behind his back. He sits before Krul Tepes and a few of her soldiers. He reflects back on Yu yelling at him to set a good example. Guren plans to make a show of resistance and then talk enough in order to send the vampires to Shinjuku tonight, where Kureto can take care of them.

The angry noble grabs Guren by his hair and raises up his face, reminding him of his place and telling him to tremble in fear. Guren spits in his face. The vampire curses and kicks him. He begins beating Guren, threatening to kill him. Guren wonders when getting beat up became so exhausting. He plans to let the vampire beat him more to make it seem more convincing.

Ferid admits to Crowley that he was the one giving the information to humans, but he says someone even more twisted than he pulled the strings this time and points to Guren Ichinose, who lies beaten on the ground.

Crowley says Guren does not look like it, but Ferid says that Guren is a namanari. A namanari is a human one step short of becoming a full demon. He says there are two beings in Guren's body, and they share their time in control. He says one half is the idealist who wants to save his friends and followers. He says the other half is possessed by the vengeful spirit of Guren's dead lover, a perfectionist who reduced herself to a demon in order to get what she wants.

Guren begins to mention Shinjuku, and his personality switches. Ferid says to watch as the real monster comes out.

Guren tells the angry noble to get his disgusting hands off of him and says he will die if he touches him again. As Mahiru possesses him, he beheads the vampire. Krul mocks his triumphant expression, and Guren draws his sword on Krul.

Guren says he is going to conduct an experiment on the Seraph of the End at Nagoya Airport and demands that Krul assists him. Krul recognizes him as a messenger from Mahiru.

Krul swats Guren away from her and sends him flying. She asks if he is a messenger sent by Mahiru Hīragi. He says Mahiru is dead and he could not save her. Krul asks who he is, but Guren only laughs in response. She says this was not part of the deal and reveals she made a bargain with Mahiru before the world collapsed. She says she cannot help Guren if he is not Mahiru. He taunts her to kill him but says she cannot. He says she has betrayed the vampires too deeply to turn back and now must make certain that the Seraph of the End experiment succeeds today. Annoyed, she kicks him. He laughs and tells her to keep up the act. Krul then shouts that the human spoke and informs the other vampires that the murderous humans are regrouping at Nagoya Airport. She orders the vampires to set out immediately.

Guren appears next at Nagoya Airport, sword in his hand. Yu is delighted, and the surviving Moon Demon Company members are shocked. Guren greets Yu and suddenly swings his sword at him. Mika intercepts it, surprising Yu. Guren tells Mika that he is in the way.

Kureto announces to Guren that it is time to begin.

Guren raises up his sword, and chains wrap around his arm as the curse consumes him. Mika tells Yu to run and says Guren has betrayed them. Yu disagrees. Shinoa also tells them to run since Guren is not acting like himself. Guren mentions drinking the blood of the sacrificial humans, the blood of demons, the blood of progenitors, and the seraph of the end. When he swings his sword, he slaughters both a vampire and a human. The chains release him and return to the van.

While Shiho is enraged at what they did to Mirai, Guren stabs him from behind. He tells him to hold still because they have not yet offered enough blood to control Mirai. Yu races to Guren and swings his sword at him but hesitates. Guren calls Yu a "little wuss" and asks why he stopped. Yu cannot believe what is happening and wants Guren to explain himself. He asks if they were Guren's family. Tears escape Guren's eyes, and he whispers to Yu to please run. Relieved, Yu smiles until Guren swings his sword down and deeply wounds him.

Yu collapses, gasping for air as blood drips out of his mouth. His wounds are too deep. While Mika and Shinoa Squad panic, Guren whispers to himself that he must continue to sleep or else this will scar him for the rest of his life. The curse marks reappear and cover half of his face.

The experiment continues, and the demon Abaddon is successfully manifested. Yu then awakens in his seraph mode. Asuramaru tells him to draw his sword. He says that Yu may be able to contain the seraph by becoming a full demon. Yu's left hand slowly begins reaching for his cursed gear. The angel yells at the humans to stop and not reach further into the forbidden.

Guren, still possessed by Mahiru, tells Yu to do it and break their taboos. He says that only someone so arrogant who desires to be loved by everyone can do it.

After Yu falls, Shinoa tries to ask Guren what is going on, but she sees Shinya point his gun at Guren and realizes that their escape is up to her now.

Guren smiles and Shinya looks on with disbelief, demanding an answer from him. He tells Shinya to not be so angry and says he is fulfilling their dream of changing the army so that anyone can climb the ranks. Shinya asks him about betraying so many of his men before realizing Guren has been possessed, despite Guren not having the typical horns, dark eyes, fangs, or rampant curse marks associated with possession. He tries to call out to Guren, but he grabs Shinya by the neck as curse marks begin appearing on his face.

Post-Nagoya Arc
Three months later, outside at the entrance to Sanguinem, vampires quickly retreat, calling for their kind and the progenitors to escape. This was right before they are cut off-screen by the appearance of Kureto and Guren emerging out onto the battlefield in thin smoke.

Cooperatively, Guren and Kureto can be seen walking and fighting together side by side against the vampires with their demon weapons. While so, both men commanded their respective demons to attack the enemies before them. On the other hand, Mirai once more appears in her Seraph form as she is being accompanied by other JIDA soldiers throughout the war. On his way back to Shinjuku, Guren injects the drug into his forearm while a soldier drives him. The drug suppresses the demon. Guren mentions having a talk with Shinya once he arrives. He meets Kureto in Shinjuku, who tells him of his plans to kill his father. He orders Guren to help him and demands he convinces Shinya to join them. He later visits him. Shinya immediately confronts him about killing his own soldiers. He draws Byakkomaru on Guren, but Guren does nothing to defend himself, which makes Shinya struggle even more. He wants Guren to admit he was possessed by the demon, but Guren insists he was in control. Shinya realizes Guren is telling the truth and falls to the ground claiming he won't be able to forgive him.
 * Anime: Another additional one month later have already gone by and that the battle at the Nagoya airport came to an end by the JIDA's successful victory against the vampires. It was during this time, further more, in which Guren himself appears standing next to Kureto in the underground vampire city, Sanguinem confirms that the JIDA has now taken full control of the place in their reign. It is then right before Kureto is about ready to depart somewhere that he signals to Guren, asking for the both of them to go and the latter does so willingly without any sort of dissent nor hostility. This is in contrast to the manga with its three month time skip and has yet to completely take over the city, Saguinem since the JIDA and vampires are still fighting each other out on the battlefield.

Osaka Arc
At Shinjuku, he meets the rest of his squad and Shinya and they complain about being locked up. Guren tells them to shut up and they must go to Osaka Bay immediately. He is next seen driving with his squad, and getting interrogated by Shinya on why he is taking them to Osaka and him killing the soldiers in Nagoya. When asked if he doesn't trust them, Guren gives a short laugh and asks if he is expected to share everything with everyone because of their friendship. Upon Shinya's confirmation and demand for him to answer, Guren counters by jokingly ask the last time everyone took a dump, which lead to Goshi getting slapped by Mito for trying to answer.

When Mito brings up how they have been like a family for eight years, Guren's expression goes blank as he recalls eight years ago on December 25, where he was willing to bring about the Apocalypse in order to revive his friends and be with them for only ten years. Shinya picks up on his expression which annoys Guren and he demands that Shinya stops trying to read him. Once Shinya stops his questioning, Mahiru manifests in front of Guren and warns him that his friends will die if they find out they were originally dead. Guren tells her to leave, which Mahiru does. Guren is still shown on the road. Upon seeing Mahiru, he swerves the car to run her over, much to Shinya's annoyance. By the end of the chapter, he and his squad arrive at Ferid's mansion. Just as Guren use Mahiru-no-Yo to knock out his friends, with Shinya being the only one to avoid Guren's attack. Mahiru manifest next to Guren, where she comments that Byakkomaru is looking to kill to him, which Guren says it's because she provoked him; as well as becomes annoyed with Mahiru's comments before the fighting starts. He deflects all of Shinya's shots before going in and slash through his body, which turns out to be a decoy. He is then tagged by Shinya with a fuda from behind, but Guren retaliates with an explosion fuda. The two then exchange punches and kicks with each other until Guren kicks Shinya to the ground. He scolds Shinya for fighting in close, though when Shinya tells him that he wanted to punch him for all of the secrets he keeps, Guren admits that he allowed himself to be hit. After Shinya allows him to keep his secrets, Guren knocks him out while ignoring Mahiru's questioning of bringing his squad (to soon realize Guren is nearing his complete transformation into a demon). He finds the Shinoa squad in the mansion's basement, and is immediately greeted by Yu's barrage of questions. Instantly annoyed, Guren whacks Yu on the head, which confirms to everyone that he is not possessed and safe to approach. Before he can tell them about reviving his friends from the dead, Yu tells Guren that Ferid already told them, much to Guren's annoyance. Shiho then asks about his sister, which Guren assures him that Mirai still lives, but does not have the power to stop the experiment done to her. When asked who is behind the experiment, Guren rules out Kureto as he is only able to command, and says that the Hīragi and the whole Demon Army are pawns to someone else.

Guren later gives background that the Hīragis held absolute power for hundreds of years which Shinoa fills in that the family committed many bad deeds to keep it. He then talks about Kureto and Mahiru doing any means to become head of the Hiragi Family, and questions Shinoa if she truly avoided this competition by asking if the demon born inside her, Shikama Dōji, talks to her. Moving on, he says that after the Hīragi heir is chosen, they fight against a being described as, "the despair that's in front of our eyes."

He later reveals that he is trying to resurrect all of humanity but only those who were killed by the virus eight years ago he tells a group that their is a method using spellcraft tomoes though it's too dense and obtuse to read, he also states that he needs Yu and he is a vital piece to the resurrection which Mika angrily denies the possibility of that. Yu agree's but thinks he is lying to him, Mika states he will kill Guren and he doesn't mind doing so. When Yu tells him that he knocked his squad he says they'd disappear if they heard the conversation and to never say that again. Yu asks about it if it hurt keeping secrets from them Guren says keeping those secrets to himself did not hurt, Yu believes it must've hurt. Guren explains to Yu he plans to use a drug on Yu repeatedly to make the seraph within him go berserk until he can control it warning him about the risks and requesting that Mika doesn't find out, only to find him close to him. Guren squad wakes up after part of the mansion breaks up by a berserk Yu which Shinya shoots him, Shinya demands who is Ky Luc once he heard about the strategy, Guren tells him a fifth progenitor.

Three days later it is revealed in a flashback the strategy to defeat Ky Luc and rescue both Ferid and Krul. Guren represents dolls with Goshi help to light them making three of them two representing Ferid and Krul and Guren holds Ky Luc doll, Narumi berates him by playing with ridiculous dolls and Crowley gives him a spare of Ky Luc doll and tells everyone that he is a fifth progenitor who's stronger than both Crowley and Ferid telling the group that he can even kill meele-type black demons wielders. He tells Yu not to interrupt him and asking Crowley if he can hold him off which he replies he might since the humans cannot take a hit, they will have to dodge as much as possible. He tells Shinya and Yoichi to shoot UV-blocking rings at them to cut them free and suggest freeing Krul first because of her strength and his plan might work if Ky Luc is stupid like most vampires but Crowley tells him he is smart and always amused commenting he is like Ferid and he will be using their trump card, Yu that not even Ky Luc would guess. As they are battling Ky Luc, Guren closes on him and summons Mahiru-no-Yo, which gives Ky an uneasy feeling and he attempts to stab Guren through the heart but Yu blocks it with his body crushing Yu's heart but it regenerates. Guren summarizes the situation to himself that they failed and Yu is at his limit and considers if he should give him a second dose of medicine risking turning Yu permanently monster or face Ky Luc as they are. They eventually succeed in rescuing Ferid..Shinya asks Guren if they won, and Guren says he was a draw: they did not kill Ky and he escaped with the queen.

He is later seen as Mika and Yu approaches him in an underground laboratory for human experiments in his residence, he admits to taking over most of those experiments after the catastrophe. Yu asks him who he took them over from, but Guren does not answer. He later takes the pair to an elaborate glowing barrier and says it is sealing a monster inside saying both the Emperor's Demons and the Hyakuya Sect joined forces to build this barrier and it's barely keeping the monster contained. He explains to both Mika and Yu about their last names and the Hyakuya Sect must have experimented on both Yu and Mika erasing their memories, Mika then gets angry shouting at Guren how long he is pulling their strings and who he is really he denies all that and tells him Saito is behind all of this since he already met him before and a vampire, the second progenitor. Guren reveals whats in the barrier which is the sixth trumpet and tells them it is a seraph and the who is continually summoning the horsemen for the past eight years.

Guren stops Mika and tells him to let Yu go as the drugs are working and would prevent him from going berserk, he explains to Mika that he and Yu were just being used for years telling him about the time Mika met Saito and about the time he is brought to the Hyakuya orphanage and reminds him that Saito is actually a vampire and the second progenitor, when Mika notes his eyes weren't red Guren laughs, Mika wonders just who is Saito which Guren responds he's been around for a very long time and doesn't know what is he plotting. When Ferid and Crowley arrives they tell Mika he was just using Guren. When Shinoa squad arrives and few of his own squad, when Shinoa approaches the barrier Guren warns her not to touch it or it will cut her arm off. When told that Mika is a Mikaela by Ferid, Guren tells him to think and go through his memories since he should know better than anyone.

With Yu engaging the Sixth Trumpet Kimizuki tells Guren to give him one of those drugs he gave Yu but Ferid gives him one, Guren later fights with Kimizuki and he asks Guren if he is going to lecture him on the fact he's now doing the same thing as Guren, Guren says he will if Kimizuki wants him to he also asks why they have to keep doing this over and over again which Guren replies because they are alive and says if Kimizuki dies, then his sister dies with him. Therefore, they must live, as they are living as families even if that require to do unforgivable or forbidden sins, after hearing that he tells Guren that he almost trusts him after saying all that.

After their victory over the Sixth Trumpet, Guren announces that they are going to take the angelic knife that came from the Sixth Trumpet in order to help humanity fight back against "millennia-old monsters."

Shibuya Arc
With their arrival at Shibuya, after the commotion about Yu being a traitor, Guren steps out of the vehicle to calm down the situation. He ties Ferid after he joyfully drives up and greets the guards by saying he's their friendly neighborhood vampire coming to attack them. Guren says that Kureto awaits them, Aoi however doesn't trust him but reluctantly allows him to enter. A guard says that only Guren, Shinya and Shinoa are allows to meet Kureto.

Inside the room where the depths of the headquarters Kureto greets Guren ignoring Shinya and Shinoa, telling him he ordered him to protect Shinjuku but he wasn't there while saying such defiance is punishable by execution Guren tells him to execute him then, since he is capable of doing it as he killed Tenri. Kureto summons Raimeiki and both Guren and Shinya summon their demon as well, Guren manages to defend himself as Kureto instantly incapacitates Shinya. As he has his sword on Guren's neck he asks him why isn't he executing him but he tells him he has a larger issue, revealing that the power he's using isn't from his cursed gear. Mahiru-no-yo sees Shikama Dōji floating behind Kureto and warns him that Kureto is nearly being possessed by an unbelievably powerful monster. Guren asks Kureto for details, he tells him after killing Tenri, the monster that's been possessing him moved to Kureto but Raimeiki is holding him off for the time being but can't hold it forever. He then orders Guren, Shinya and Shinoa to save him if they can however they are to kill him if he goes insane. Guren later visits Shinoa in a hospital bed where she was being monitored, explaining that she fainted and what happened he explains to her that she, Kureto, and Seishiro are all being examined because the demon who possessed Tenri Hiragi is now on the move. He asks Shinoa if her Scythe has anything to do with Kureto's condition, she tells him that the thing possessing Kureto is also trying to possess her and adds that it might've possessed Mahiru in the past when she gave up her life and her relationship with Guren, in order to save her, he notices Mahiru manifest, and tells Shinoa to get some sleep. She inquires if he wanted her to offer some restitution for ruining his relationship with Mahiru, and he replies that the past is past, and the catastrophe still destroyed the world, which does not matter anymore, since it is never coming back, and what is important to focus on their current situation, to which Mahiru complements his speech. After Guren exits the room, it is revealed that the entire room is actually a laboratory of the Demon Army. He later approaches Kureto, and Shinya tells Guren that Kureto is a masochist and both of them tease Kureto briefly. He tells him about Shinoa situation that Shikama Doji is affecting her but she isn't bothered by it at all, and adding that it went after Mahiru before, he elucidates that Mahiru protected Shinoa until she became capable of handling it herself. Kureto questions him if there is a way to prevent it from taking over but Guren answers he will still save him even if there isn't. Guren is approached by a tied Yu and Mika and queries him if this is a lab.

When Yu is confused at the situation Kureto's in, Guren explains to Yu that he is being possessed by an unknown monster, that is also likely possessing the other living Hiragis, including Shinoa. He later hears Shinoa's call for help to save Yu then she tells him about Shikama Doji made contact with Yu. Shinoa is later being carried in a stretcher with her squad by her side and Guren announces that her heart isn't beating much to everyone shock and Yu desperately asks for help.

Unable to do anything as Shinoa is transforming into a vampire Guren listens as Yu explains to Kureto that the monster seemed to know him from some time ago. Guren does not react as Yu is taken away (somewhat willingly as he wants to help Shinoa) on Kureto's orders. but then remarks that Kureto sure recovered fast. With Mahiru-no-Yo levitating behind him he talks to Kureto about how Shikama Doji went after Shinoa despite Kureto being the head of the Hiragi family. Under the impression Yu is his favorite soldier, Guren is then questioned about him, but says he has no information. He does divulge that is was actually Mahiru who found Yu, since prior to her death she worked with Saito who was at the Hyakuya Sect. Guren is queried by both Shinya and Kureto with them wondering why he did not tell him anything. He never told Shinya having his reasons, and has not said anything important for Kureto to know, only hinting if he did tell it would lead to something extremely disadvantageous to everyone here. Guren rebuffs Shinya's attempt at a reconciliation when he suspects it is related to what happened eight years ago, telling him not to pry or close the distance. Guren is fully aware that Shinya would turn to ash if he discovers he has been revived, and only shares that nothing good would happen. Guren receives several more questions from Kureto ranging from vampires, curses to human problems but Guren brushes them off and points out they are all part demon now. All he does know is Mahiru said Saito was "after it", he says he can probably tell Kureto that but does not know Saito's goal. Remaining silent at what his own goal is, Guren does have one question answered for himself: when asked who is possessing him and who or what he is imprisoned by, Guren hears from Mahiru-no-yo that he is possessed by love and imprisoned by friendship while she is embracing Shinya.

He finds Mika following Yu, tapping him with his sword he asks where Mika thinks he is going. Guren laughs off Mika's claim of going to the bathroom knowing vampire's do not have that function anymore. Suspecting correctly that he intends to take Yu, Guren asserts he is not and that he himself is trying to save Yu from the curse he carries. Asking where he would go he points out Mika has no allies, and no plan for the first. Guren denies Mika's accusation that he is a puppet of the first, and states he has spent years trying to get out from under the Hiragi family and it's curse. Guren is sure that Mika has no choice but to trust him, however Guren is suddenly attacked by Mika. Blocking his sword, he states it is pointless, Mika is alone here. Guren instructs Shinya to end the clash. Along with Kureto the three of them are able to leave Mika on the ground disarmed. After Mika's actions, Guren tells him to stop his tantrum, he is alone without Yu, and anybody who is alone is just an easy picking. Guren uses this chance to get him to join them, using Mika's desire to keep Yu safe as leverage to get him to cooperate. Restating they are not the first's puppets as well fails, with Guren unable to provide the proof Mika asks for. He cannot say for sure if he is not somehow betraying everyone since the foe they are up against is practically a god. Turning his attention to a plan for the first with Guren having tons of friends here who he does not intend to leave behind, he asks Shinya and Kureto about their opinions. After some bickering of which Guren has not the time for, he says that Ferid and Crowley are fighting the First Progenitor. As he considers what happens if those two go down, he see's Ferid appear and is simply told to run now. The group is surprised by Shinoa's reveal, who is very interested in what is happening. Daunted by her arrival, Guren can only comment on how bad this is before being beset by multiple levitating scythes.

Guren and Kureto try to defend themselves from the scythes that are attacking them continuously. When asked by Shinya what to do after Shinoa ceases her attack and smashes her way out the building window he remains silent. Mahiru-no-Yo manifests and tells Guren the time has come as of now Saito and Krul will arrive. Just as Mahiru-no-Yo tells him it's time to betray everyone as they planned which Guren complies to.

Not taking part in the defence from the Hyakuya Sect's invasion, Guren remains by himself as he is urged by Mahiru-no-Yo to betray everyone, while he listens to her silently. With it time for their betrayal Guren is encouraged to let himself change to become the other Guren and he close his eyes.

Asked by Mahiru-no-Yo if he is ready to turn into a full demon, Guren asks what if he says no. Not emboldened by the encouragement, Guren contemplates that if this fails then everything would be much easier and considers whether it would be because he could escape his responsibilities. Labelled a weakling, he asks what is wrong with that and states he is not crying. Guren does say that he is scared, and thinks that it began back when he was five years old. Remembering when he first met Mahiru, he thinks that was the day he learned to hate how weak he was, and how powerless he was to protect the ones he loved as Mahiru was led away right before his eyes. Guren told himself someday he would have the strength he needed to keep the people he cared about safe.

He explains to Mahiru-no-Yo that even now he still cannot protect a single person recalling how his father was executed right in front of him and Mahiru had no one to help her ever so she has no choice but to become a demon. He thinks of Shinya and the others as nothing more than walking corpses and when their time is up they will die a second time. Besides what is more worse is he had to trigger the catastrophe to bring them back to life, sacrificing every human being in the whole world. Guren is not soothed by Mahiru-no-Yo's words that the apocalypse would have happened anyway. Hearing that if he did not instigate it, someone else would have, Guren picks on the word someone since it was him, angered by his actions he blames himself more shouting aloud. He is then hugged by Mahiru-no-Yo and told it is both their fault.

Told not to worry and that he will succeed, Guren grasps the hilt of his sword and as he starts his transformation into a demon, chains materialize behind his back. He does not react to Mahiru-no-Yo encouraging him in this, neither to Shinya arriving and calling his name, or shooting some of the chains. Guren's skin darkens with him holding half of the demon now. Not responding to Sayuri calling him, Guren is told by Mahiru-no-Yo to close his eyes. Inside his mind he see's an unconscious Mahiru-no-Yo's with Guren's sword stabbed through the chest. Guren watches unfazed at the sight of her screaming as a hand rips through the body with another being emerging from the wound. Not answering Noya on how long it has been since he kept him bound there, and not to Noya laughing to himself, Guren states his name and is then tempted with power to make woman his, power to kill his companions, and destroy everything he hates. Receiving his sword, Guren is enticed by Noya's offer to become the most powerful demon who ever lived.

With Mahiru-no-Yo separated from Noya, waves of energy are emitted by Guren as he turns into a demon with two large horns. With his squad meaning to restrain him, he raises his hand and tells them not to move, he will crush them. Doing that anyway, he telekinetically pins them to the ground with a compressing force, Shinya included. Guren is visualised by Byakkomaru as he discusses with Shinya on abandoning Guren.

Seeing Shinya turning into a demon with the desire to never give up on Guren, he seemingly effortlessly deflects Shinya's attacks. The response to Shinya telling him to look at him is to swing his sword and send Shinya crashing into a wall. With Shinya determined to save Guren, remarking that he will not let Guren leave just as Mahiru did as well as staying with him and his squad fighting together, Guren replies that Shinya cannot stop him. Despite all what Shinya says, Guren simply states that he is not Guren anymore and then stabs Shinya through the chest. He answers Shinya's question that he is a demon, before proceeding to say that he will like always let himself drown in his own power to save him.

He approaches the spirit of Mahiru and Noya, both of which who appear in the air before him. Guren announces that he thinks he will start by borrowing a little power and unleashes chains which sap his squads strength to increase his own. Raising his sword, he calls upon Mahiru-No-Yoru and projects energy to join that coming from Noya and Mahiru. With his sword enveloped, he walks to the exit telling Shinya that he goes to save the world.

Coming across Yoichi and Shiho who is carrying an unconscious Mirai on his back, he apologises to Shiho stating he needs to kill Mirai. With his overwhelming speed he snatches Mirai away and kills her instantly by stabbing her through the chest. Retrieving the sinful key that surfaced from Mirai's body, Guren praises Yoichi for his action of knocking Shiho unconscious. He comments on Yoichi's sister's body being in storage before leaving as Yoichi attacks. Arriving at the battle between Saito and Shikama Doji, he brushes off Saito's comment on him being late remarking it is not his problem that Saito almost died. He is defended by Noya and Mahiru-no-Yo who have halted a scythe that Shikama Doji aimed at him. Tossing his sinful key to Saito, Guren then surprises Shikama Doji by attempting to flank them whilst distracted before telling Saito to hurry up with attempting to seal Shikama Doji.

Showing surprise at Saito betraying him as he is almost bitten from behind, Guren came prepared so counters with Ferid's assistance using Jigenso's portals to deal with Saito. With the help of Jigenso, Guren along with Noya and Mahiru-no-Yo each acquire an sinful key and surround Shikama Doji using a sinister power to constrain Shinoa.

Continuing to hold the sinful key as it restrains the first, Guren responds to the first’s concession to let himself be sealed for the time being by asking how about he make it an eternity. Ignoring Noya’s suggestion that they kill her and be done with it, and Shinoa’s question on whether he is a demon, Guren leaps away. Locating Yu tied to a stretcher, Guren slices through the guards who were trying to transport him to Shinjuku.

Disregarding Yu's request to cut him loose, Guren tells him not to worry about his demon state. Asked if he is all right, Guren answers that is a good question as he feels his strength seeping away with the life-absorbing barrier reaching its end. Aware he is almost out of time, Guren needs to finish everything whilst he still has the power. Refusing Yu's appeal to be freed, Guren binds his mouth and states he will stay like that for now. Activating his cursed gear, he releases Noya. Standing beside Noya as Yu and Mika discuss their next move, he asks Noya if he is going to help get his wish that he has desperately clung onto for a long time. Not trusting him since he knows Noya has his own plans, Guren then silences the demon. Listening silently as Yu proclaims Mika to be his reason for living Guren remains unmoved with Yu's desire to rescue him. After Yu transforms into a demon himself, Guren smirks then informs both Yu and Mika that they are not getting away and with his blade he attacks them both.

Whilst his sword is blocked the impact blast across the cityscape and sends Yu and Mika flying. Not satisfied with the extent of the power, Guren contemplates his sword and notes that the life-absorption barrier is getting weaker and weaker. Furthermore, with him splitting the strength between his two demons he comments no wonder his strike was so flimsy. Knowing Yu and Mika can get past the wards, there is no need for Mahiru to cut off their escape route so he orders her to return to his sword. After some teasing from Mahiru, he tells her to hurry and is granted more power.

Guiding Noya that they are going after them, Guren catches up and lands right in front of Yu. His attack aimed at Yu's neck instead connects with Mika's back as he defends Yu. Guren watches Yu jump backwards taking Mika with him and escaping. He answers Noya that they got away again because he took too long to get here. Later Guren notices explosions and streams of dark energy flow out of a building. Smashing though the wall where Mika and Yu are, Guren taunts them by saying they are having fun before informing Mika that both of them are not getting away this time since he is going to capture them right here. Idle to the swords that are targeting Noya that have left him with severed limbs, Guren asks if it was Yu. Told it was Ashera who is using spells Noya has never seen before and working with his human host, Guren laughs that Noya got beaten and is suddenly all excuses before having him return to his sword. Powered, he locates both Yu and Mika and answering his demons he is ready to do this he faces Yu and Mika in a fighting stance.

Noting the two empty sheathes levitating on either side of Yu, Guren wonders what sort of new demon power is it this time. Not seeing but sensing a presence behind him, Guren swipes away an invisible weapon that has still managed to faintly scratch his cheek. Licking the blood, Guren thinks if he wastes energy trying to spot them he is dead. Having them sliced away, he says for Mahiru to auto-block the unseeable swords and that is going to use spells. Addressing Yu, he questions whether after letting his demon possess him that this is all he can manage, before reacting surprised at Yu's Asura-kannon, infinite blades, knot of fate conjuring a gigantic circle of katanas around the building. Guren can only sense that they are all there and coming for him, also his own demons are telling him they cannot dodge all of them and to fall back.

Guren is seen trying to cover himself as he is stabbed by multiple swords. but this was an illusion as the spell tag damaged by the weapons breaks. Answering Mika that it is a good question where he went, Guren appears behind Yu and Mika's backs to place binding spell tags on them. Grabbing Mika's arm and telling him to quit struggling, Guren produces a syringe to weaken the demon. Aiming it towards Yu's neck, and having it stab into Mika's hand as he protects Yu, Guren orders Mahiru-no-Yo to return and crush Yu's heart. With his sword stabbed through Yu's back, Guren tries again with the needle and successfully injects Yu to weaken his demon. Now intending to deal with Mika, Guren instead finds him biting down on his shoulder and having his blood drained. Pulling his sword out of Yu's back, Guren strikes Mika's head with the hilt and damns him as a vampire since he has lost too much blood. Approaching Mika against the wall, Guren says he is not going to let Mika draw upon more power for himself and raises his sword. Registering that Mika's counter-measure would be bad, Guren anticipates the arc that propels its way outwards and tears its way through buildings.

Post-Shibuya Arc
Later Guren is walking alongside Noya and Mahiru. When Noya was experiencing an extreme pain in his ears Guren informs him that it is the death wail of a vampire that it's a powerful shriek which only other vampires can hear. Guren remains silent when Noya questions what he injected into Mika's hand during their fight, and if this is his and Mahiru's doing. Similarly Guren stands unresponsive as he is injected with a substance from Mahiru. Guren then orders her to shut up and finish it. After Noya is rendered unconscious, Guren alongside with Mahiru comments that vampire Mikaela has died and now he is transforming into a Black Demon as the both of them watch the sight. Guren is mentioned by Yu as he happily recounts the fight they had. He is visualized when Krul mentions Mahiru as the one who formed their current plan.

Natural abilities
Adept with prior knowledge of the experiment since he was a teenager, Guren has proven himself to be an intelligent scientist, capable of developing Cursed Gear during adulthood. Due to this, he has even managed to create a method that comes with a very high rate of success for the development of humans who can bear Black Demon Series weaponry. Guren is also an exceptional strategist and leader, with him being typically the leader of any team he is in. He is known for having backup plans, such as giving Yu the drug to activate his Seraph genes in case they were cornered. He is very analytical and able to quickly deduce how to counter the current predicament, such as ordering the group to retreat. He is also courageous and loyal to his friends, even to the point of ordering Shinya to abandon him and take command for the group in his stead, so they can escape, while carrying on with their mission. Back when he was still a teenager, even Kureto acknowledges the great intellectual, political-like nature of Guren's capabilities, to the point that having known each other at the span of about eight years, Guren was his right-hand man in carrying out his missions. Guren is also adept with his knowledge of the five-man battle formation called Moon Demon Company, which is mainly used as a tactic for defense within his squad. He is highly proficient in deceiving others, as shown by how no one, not even Shinya, with only Kureto and Ferid being the only individuals aware, knew of his demonic personality until he revealed it himself.

Guren is an outstandingly proficient combatant, specializing in many forms of combat, particularly swordsmanship. Born with outstanding talent among the Ichinose Family, Guren's combat skills marks him as among the finest fighters in the army and he can easily hold his own and triumph in a fight even against those with superior physical power, or other highly skilled fighters with great might. This was shown when Guren is able to kill several common vampires with a single strike and can fight Mikaela evenly, who has the blood of a third progenitor and wields a first-class vampire sword. Indeed, with assistance from his squad, Guren almost came close to defeating Mikaela had Ferid not came to his rescue. Later on, Guren calmly overwhelms Mikaela even after he fully became a Vampire, with the power of his Cursed Gear aiding him. During his teen days, Guren once managed to evenly duel Kureto while apparently holding back as Kureto himself said, with Kureto having to use the full power of his Cursed Gear to overpower him, at which he still put up a brief fight and was able to slice off Kureto's arm. Another instant is when he bypasses Yūichirō's defense in the mock battle to get to his squad members, defeating both Shinoa and Mitsuba first despite it being her five-men squad against a three-men squad (excluding Goshi, Sayuri and Shigure).
 * Anime: While slashing each and every one of them with his sword, Guren can easily repel away the decoys set up by Mitsuba's demon weapon ability at a quick succession. Unlike in the manga, where a sword fight between Guren, Yūichirō, and Shihō never occurs, it actually happens in the anime. Guren was able to easily fend off both of them at once simultaneously and then low-kicking Shihō away while handling Yūichirō on his own with little effort even though he calmly praised him for his improvements.

He is also highly proficient in martial arts, often implementing hand-to-hand attacks effectively while engaged in swordplay to easily batter aside enemies. He fairly quickly defeated Shinya in hand-to-hand and even could dominate Mikaela as a true Vampire wielding his sword while greatly empowered physically by Mahiru-no-Yo for a while using only his bare hands.

Guren also specializes in other combat assets such as the use of magic and spell tags, known for having particular abilities in it even among the Ichinose Family and he is proficient in using it strategically in combat. Guren also holds great knowledge in spell casting, as shown by how he was able to see through one of Goshi's illusionary techniques and anticipated Mito's Vajrayaksa Curse before easily countering it.

Since he isn't an ordinary human anymore, Guren was able to fully recover one of his cut-off arms, and survive powerful vampire attacks from the seventh progenitor, Ferid Bathory, both when they met when he was sixteen, and later, on the battlefield as an adult which surprised him.
 * Anime: The possessed Guren is able to move at a remarkably, insane speed even though his monstrous movement was shortly anticipated and then apprehended by the third progenitor, Krul Tepes, pinning him down on the ground in defeat. The physical prowess bestowed by the demon weapon, Mahiru-no-Yo in this state proves so great that Guren could casually overwhelm Mikaela in terms of physical power, despite the large boost he acquired for becoming a true and complete vampire, as well as wielding a first-class vampire sword (though at the time he had not fortified himself by having it drink his blood). In addition to overwhelming Mikaela in their exchange, he also could lift Mikaela by one of his feet, and then throw him to Yu, causing both of them to tumble down into the ground. It was while Guren is also fighting him hand-to-hand in close combat to his own advantage for a very short period of time.

Magic and Spells

 * Fudo Myo-o spell: Guren is capable of skillfully using enchantments on spell tags and talismans since late teens. It is shown even at the age of 16, he can implement a talisman on the sword to augment the weapon's cursed power and ability. As a result, from synchronizing the talisman with the blade itself, this created an explosion to unnaturally occur on the enemy's body for physical damage. While so, he can also successfully implant one of these spell tags on the targets' head whenever they're caught off-guarded or if the chance presents itself. In such cases, for example, this type is an ancient one that causes an explosion to occur right after a few seconds has merely gone by before detonating.
 * Illusion spell: While fighting the demonic Yu, and Mika as a demon himself, Guren used a spell that allowed him to create an illusion to trick them so he could get close to them. The spell was notably convincing enough that Mika, who could see through Goshi's illusions, could not notice it, but not enough to trick Yu. Guren uses one in particular illusion like to strategically serve as a distraction in his battles against Yūichirō and Mikaela. Further more, the Ichinose family and particularly Guren himself had special incantations such as a talisman placed on the scabbard of his katana. When he activates the incantations through a talisman for the blade, it begins to make the sword glowed brightly crimson, red in color.
 * Anime: Unlike in the manga, where Guren was able to use a spell tag on Mikaela to create an explosion upon range, it also causes the ruined building to start sinking into the ground below with a gust of whirlwind blowing by its surrounding vicinity. Additionally, Guren can be seen explosively bombarding the thirteenth progenitor, Crowley Eusford with multiple spell tags the moment it came into contact with him yet the latter remains undamaged from the attack.
 * Paralyzing spell: Guren was able to paralyze both Yu and Mika by placing talismans on their back.

Equipment

 * Kujakumaru: This blade goes by the name of Kujakumaru and is already wielded by Guren Ichinose at the age of fifteen. It was a Guren wielding Kujakumaru LN.jpg heirloom that had been passed down from generations in the Ichinose Clan. Kujakumaru was a sword that had been sealed with the curses of those who had been beheaded by it. The sword was able to prevent the enemy from absorbing the impact of an explosion created by a talisman he put in place on his blade, which was supposed to resist any of the Hīragi Family's curses. Once the seal had been lifted, the enemy will soon become cursed by this weapon, turning their body red. As a result, the curse will eventually destroy the enemy's body, causing it to have their flesh be torn apart and atomize. Mahiru cuts the sword in half during their first battle.


 * River's Edge: An enchanted blade owned by the Ichinose Clan. After Mahiru destroys Kujakumaru, Guren begins using this sword in its place. When Kureto captures and interrogates him, he takes this sword and returns it to the Ichinose Clan and gives Guren Hoarfrost instead.


 * Hoarfrost: An enchanted katana that Kureto gives to Guren after he swears loyalty to him. It vibrates and emits a high pitched ring when Guren drew it from its sheath and was then filled with the desire for slaughter and bloodshed. According to one of the many tales about the blade, it cut down a thousand demons in a row without getting a single nick.

Cursed Gear

 * Noya (ノ夜): A demon who formed a contract with Guren, given to him by Mahiru and becomes his demon weapon in the form of a black katana. Guren can call Noya fly back to his hand whenever they're separated. With the recent revelation, Noya is a possession-type demon of the Black Demon Series as it mainly concentrated on enhancing Guren's physical abilities similar to Mahiru-no-yo as Noya can increase Guren's strength by using his desires as sustenance. Noya eventually transformed into Mahiru-no-Yo due to Mahiru merging with the demon. However he later managed to erupt from her body and make use of Guren into becoming a full demon.
 * Mahiru-no-Yo (真昼ノ夜): A possession-type demon of the Black Demon series that Guren wields in the manga. The weapon is still a black katana, like Noya, but now has a glowing, crimson red, streak that is outlined down in the middle portion of it.Glen's Demon Possession.png Mahiru-no-Yo can significantly increase Guren's physical abilities, and calling out her name would increase his power even more so. If Guren wishes to, he can invoke the demon's real name to have her possess him. This would cause Mahiru's apparition to appear and enshroud the blade and the arm wielding it with streaks of overwhelming flames. Guren would would be able to launch these flames at his opponent with one slash, and is strong enough to engulf an explosion in the midst of its vicinity.

Additionally, Guren can utilize the power of the demon weapon for other miscellaneous purpose such as filling areas like the classroom with its immense demonic auras. Within the power's vicinity and range, victims pass out unconscious on the floor if they don't have the strength or willpower enough to overcome it. However, if the targets have high psychic resistance, used wards, or are a potential candidate for the Black Demon Series, they're not any bit fazed by Mahiru-no-Yo's demonic aura. Merely drawing the katana from its sheath alone seeps blackish gases made from within in and out of the blade.
 * Not only does it strengthen his own abilities and power physically, Mahiru-no-Yo can also be used to devour an enemy's attack. If Guren was on the defensive side, he would then call on the demon blade's name to assist him in battle when he was knock far back and being sent flying to the ceiling. He will then used the demon's power and ability to cushion his physical impact for safe landing. This was only while the appearance of demonic auras became visible from behind Guren, materializing onto him little by little in sparks.
 * Once Guren is possessed by Mahiru-no-Yo, the blade would seem to have a mind of its own. The blade unsheathed itself from the scabbard and then proceeded to move around on air swiftly, beheading the noble vampire. In the manga, it was right after that did Mahiru appear as a ghostly apparition with mass-like demonic aura, hovering over Guren while his katana is equipped under her. Whereas in the anime, however, it is portrayed differently with Mahiru's facial appearance seen and later handing down the weapon back to Guren's possession.
 * Anime: Guren would go on and further use the power of his demon weapon, Mahiru-no-Yo to summon forth a red whirlwind cloaked with thin layer of crimson-like demonic aura. More so, the demonic aura can be seen concentrating all around its inner layer and then being destructively launched at targets through him up front within his range. This red whirlwind was able to demolish the concrete wall of a building, pushing back the likes of Yūichirō, Shinoa, and Mitsuba and leaving them at a standstill temporarily.
 * In contrast to the manga, when Guren spoke of drinking the blood of human sacrifices, demons, and the progenitors, his katana drastically underwent a sudden change of color scheme. Through doing so, the katana itself went from being almost black in color to purely red of throughout the blade's length as is shown on the cover for manga volume 8. Furthermore, the transformation of his demon sword's color scheme is almost identical to that of a first-class vampire weapon, as those used by the progenitors, when they allow it to drink their blood, giving the blade a deeper shade to red as well. Something similar occurred when Guren used a talisman to turn the color of a non-cursed gear's blade crimson, from the light novel series. In the anime, however, he managed to change a cursed gear weapon's color scheme from that of the Black Demon Series, into fully red without placing any sort of talisman on it.

Demonic powers
After becoming one when Mahiru and Noya separate, Guren receives a vast increase in power and is noted to be no ordinary demon. His physical strength and speed increases to the point where he can easily deflect all of Shinya's attacks in his own demon state and soon defeat and severely injure him, blitz Kimizuki and Yoichi and easily kill Mirai before they could react and overpower Mika and Yu's guard with a single slash and sending them flying, cutting through several buildings, despite not being at full power by that time. His endurance and stamina is such that he was able to endure Mika forcibly biting and draining him of much of his blood and remain conscious. He can release an overwhelming pressure capable of easily pinning down his whole squad completely, although Shinya was able to offer some resistance, and chains capable of draining power from them.

Book 1
"When I was young, I was sure all of my dreams would come true. I could be with the person I love. I could have the things I wanted. I could live happy. It all seemed so easy. It really did."

- Six-year-old Guren's point of view.

"She was sitting so close I could hear her breathe. I liked the sound. I liked her voice. I liked listening to her heart beating next to mine. I liked everything about her."

- Six-year-old Guren's point of view

"I belonged to a lowly branch clan. But from my place, down in the dirt, Mahiru shone like the sun."

- Six-year-old Guren's point of view.

"…Power. I’ll never get the things I want in life…unless I have power."

- Six-year-old Guren's point of view.

"Haha. Actually, I said it because you two are underestimating the Hiragi Clan. I’m gonna repeat this one more time. Don’t get reckless. Not even for a second. We have to be on our guard at all times. Apart from us three, no one at this school is loyal to the Imperial Moon. They’re all enemies. Every single one."

- Guren to Shigure and Sayuri.

"I decided before today that any opponent who sees my full strength needs to die. I’m giving you five seconds. Go back to your masters and tell them the Ichinoses won’t play ball. I’ll count: Five…Four…Three…"

- To Makoto Kijima (Saito).

"You’ve grown up. You’ve become strong and beautiful."

- Guren to Mahiru.

"There it is. 'The end of the world.' The Thousand Nights is just another fly-by-night cult, isn’t it? Let me guess: Only true believers, who join your religion, will be saved. Am I right? Our clan pulls the same kind of tricks. So do the Hiragis. Everyone as the same gimmick. Did you think that was all it would take to trick me into joining you?"

- Guren to Saito.

"I know better than to trust someone who can’t keep his trap shut."

- Guren to Shinya.

"For my part, I’m not interested in being a puppet for the Thousand Nights. I’ve already had enough of bowing my head. My answer is right here! I’ll destroy anyone who tries to control me!"

- Guren to Saito.

"Kujakumaru…release!"

- Guren summoning Kujakumaru.

"Look at what’s happening to you, Saito. Do you know why you’re glowing red? The curse is feeding on you. The curse changes you, and then it devours you. Once it has finished consuming you, you’ll be trapped for all eternity inside the sword."

- Guren to Saito.

"I think you’ve gone mad. Tell me, how many people did you sacrifice to create that blade? How many lives were lost to your experiments?"

- Guren to Mahiru.

"Hmph. I don’t know why you’re acting so friendly all of a sudden, but I don’t think I like it."

- Guren to Norito.

"You’re right, I’ve got no reason to thank you. What I was gonna say is, just stay away from me. I don’t need any friends."

- Guren to Mito and Norito.

Book 2
"I’m patient. I was born that way. Unlike a certain brat I know who takes every chance he gets to show off."

- Guren to Shinya.

"Tell her I don’t like being manipulated. By anyone. Tell her that she’s a fool, and if she really thinks she loves me she should stop playing games and tell me what she’s planning."

- A message to Mahiru.

"...betraying the Thousand Nights…the end of the world…our destinations are the same… This is all starting to sound like some grand romance novel. What are you planning, Mahiru…"

- Guren's thoughts.

"…Ngh. You son of a bitch. Why did you even spout all that stuff about wanting to see who was stronger?"

- Guren to Kureto.

"I don’t care about you enough to bother laughing at you."

- Guren to Mito.

"So I’m actually strong. So what? What difference does strength make when you’re born an Ichinose? You’re from the great and mighty Goshi Clan. And that redhead back there is an esteemed Jujo. But what am I? As far as the Hiragis are concerned, I’m just an Ichinose mongrel. No amount of strength can change that."

- Guren to Norito.

"I know you’re ready to sacrifice others. Aren’t you? Mahiru…"

- Guren's thoughts.

"What you should really be angry about is how weak we are. They can torture us and we don’t even have the right to get angry about it. They almost killed my father. It’s not the Hiragis who are the problem. It’s our own lack of power."

- Guren.

"You don’t have to protect me. I don’t need to hide my strength anymore."

- Guren to Shigure and Sayuri.

"Of course, the Hiragi army is a pack of fools. It’s possible the area’s been poisoned and they all just marched in to their deaths without noticing. If that’s the case, then there may not be enemies on the ground after all."

- Guren.

"And what do you propose we should do? With so little information, any in-depth strategy will just trip us up. We can spend all the time we like talking about what we think might happen and how everything should play out. But we can’t get wrapped up in some foolish plan based on wishful thinking. What we need to do is kill any enemy that shows up. And if we can’t kill them, we need to at least try to make it back out alive."

- Guren to the squad.

"As squad leader I only have one order for you. Drill this into your heads. I don’t want you to think of anything else. Nothing else is important, do you understand? The order is…don’t die. No matter what else happens, do not die. Ready… The mission has begun."

- Guren to the squad.

"Mahiru… You’ve got to stop this research into cursed gear. It’s no good. This is the kind of power that will make fools of us. It will control us."

- Mahiru to Guren.

"We’ll think of another way. There’s got to be something else, another path…"

- Guren to Mahiru.

"This time, I’ll protect you. Come with me, Mahiru."

- Guren to Mahiru.

"Hmph. Haven’t you ever heard of 'The Tortoise and the Hare'? If you keep rushing forward at this pace you’re going to destroy yourself."

- Guren to Mahiru.

"I can save you now. Throw away the sword and come with me."

- Guren to Mahiru.

"The war began for me when I was just a little kid."

- Guren.

Book 3
"If we start conducting human experiments, where will it stop? New magic, new research, new powers. Power, power, power…. And then what? What happens after we turn our own comrades into human guinea pigs? Will we be swallowed whole by our own lust for power, or will the Hiragis crush us beneath their boots? Either way, it’s a disaster in the end."

- Guren to Mitsuki Iori.

"I want you to avoid human experimentation as much as possible… If we’re going to do this, we’re going to do it with our reason intact."

- Gurn to Mitsuki Iori and the other Order of the Imperial Moon Aichi scientists, giving them permission to study the demon’s infection.

"Hmph… So an angel is going to alight at Christmas, trumpet in hand, to kick sand in the world’s face? You gotta be kidding me. This is modern-day Japan we’re talking about."

- About Mahiru’s prophecy.

"At your level, do you think you’d even have the chance to kill yourself? Don’t underestimate the Hiragis. If the two of you knew what was going on, I would never let you leave this compound again. I’d find two other guards to serve me. Do you understand? If you want to stay by my side, then keep those ears covered."

- Guren to Sayuri and Shigure.

"What can I say? I’m just a loser, born and bred. I’ve always got to watch out for who’s going to kick me next."

- Guren to Shinya.

"Jokes are supposed to be funny. I guess you’re so used to being kissed up to that it’s rotted your brain."

- Guren to Kureto.

"I guess I can trust you a little after all…"

- Guren to Shinya.

"No, I am going to save you."

- Guren to Mahiru when she begs him to kill her.

"We’re together right now! I’m here, with you, right now!"

- Guren embracing Mahiru.

"For now… I don’t want you leaving my side. No more talk of things being too late. I’ll find a way. I’ll save you…"

- Guren to Mahiru.

"Dammit… Just be quiet. Isn’t it obvious how I feel? Look at what I’m doing. You know I shouldn’t have come here. You know I shouldn’t be touching you. So why do you think I’m doing it?!"

- Guren to Mahiru when she asks if he still loves her.

"Don’t ‘maybe’ me! Come out of this alive and you can figure out how you feel later. Love won’t mean shit if you die!"

- Guren to Mito.

"Ha… Haha… Ahahaha… Okay, Mahiru, I get it. I give up. I’ll become a hare, too. A demon. But I won’t be like you. I won’t give up everything. I won’t stop being human."

- Guren to himself.

Book 4
"I’m giving up my humanity so that nothing else will be lost!"

- Guren to himself.

"If the outcome is the same either way, then I choose to move forward."

- Guren to Noya.

"Rrrraaaaaaa…. Hahahahaha… Blood… Give me blood… I’ll kill them all! I’ll kill everyone who gets in my way!!"

- Possessed Guren.

"What’s the point of trying to deny the truth with your little fuda? Those desires inside you, those are the real you. You can’t deny that!"

- Guren to Shinya.

"So? My life should have ended today. So what if I get betrayed in the future? What other lives do I have to lose?"

- Guren to Noya.

"I told you I would protect you. But I can’t. I’m too weak. It’s my fault. But…at least, we can die together."

- Guren to Mahiru

Book 5
"That’s not true! This isn’t your fault! Goddammit, Kureto! Quit fucking around! You don’t need to do this. You know I’ll act! Let my father go right now!"

- Guren to Sakae and whomever is listening in.

"We won’t let them execute my father… We’re going to do everything we can in these next two days to eliminate Mahiru."

- Guren to Shigure and Sayuri.

"I started regretting things a long time ago."

- Guren to Kureto.

"Even as I am… I have friends who believe in me. I won’t betray their trust."

- Guren to Noya.

"If you’re not one of my friends, then become one. That’s an order. I want you to be my friend."

- Guren to Noya

Book 6
"What do we have to live for? …We’ll never be more than slaves. No matter how hard we try, nothing ever seems to go our way."

- Guren to Sakae Ichinose before his execution.

"Dad! …I’m proud that I was born your son."

- Guren to Sakae Ichinose immediately before the execution.

"I can do this, Dad… Don’t worry. I can do this. I can be the son you hoped I would be. Just keep watching over me."

- Guren to his father’s decapitated corpse.

"Then, I’ll tell you the truth. What your father said is true. We’re dirt. Accept it. It can’t be helped… But that’s only temporary. So no more complaints. Shut your mouth and follow me, got it? You do that, and I’ll lead you to that better future you’ve been waiting for."

- Guren to Makoto Narumi.

"You’re included in the list of people I want to protect."

- Guren to Mahiru.

"Listen up, everyone. I’m going to try contacting Mahiru now, to ask her for help. Chances are, the Imperial Demons will be tapping the call. So even if we manage to stop the world from being destroyed, we’ll probably be accused of treason for what I’m about to do and be put to death when this is all over."

- Guren to his squad.

"I thought that’s what you would all say. If we make it safely to Christmas, let’s spend it together, playing video games and eating cake. Chocolate, marron glacé, and strawberry shortcake."

- Guren to his squad.

Trivia

 * The writer, Takaya Kagami, thinks of Guren as "The Unparalleled Ichinose!" while writing him.
 * Guren 「紅蓮」 means "crimson lotus."
 * Ichinose 「一瀬」 means "one rapid."
 * He is one of the first characters designed, along with Mikaela and Yūichirō.
 * The volume covers have humans on odd-numbered volumes and vampires on even-numbered volumes. Guren is the only member of the Japanese army to appear on an even-numbered cover so far, which was actually a big hint that he had been working with the vampires all this time.
 * In chapter 14, Kureto promises to give Guren a reward for his efforts in Shinjuku. Takaya Kagami's Q&A revealed that it actually turned out to be chocolate ice cream.
 * In the popularity poll, Guren earned 4th place at 3,307 points. In the 2019 popularity poll, Guren ranked at 4th place with 3,616 votes.
 * There was already a demon inside Guren's heart before he even made a contract with Noya.
 * According to the Manga 8.5 Fanbook:
 * Interests and Likes: [Interests] Yūichirō/Mahiru [Likes] Games/Jazz
 * Favorite food: Curry
 * What he looks for in the opposite sex: Mahiru Hīragi
 * Comments about him:
 * Shinya: "Guren is a pretty shy person. Although he really likes us, he’s not very straightforward about it." 
 * Kureto: "That guy works well. He appears to be doing something under cover, but I’m planning to capture him as a hostage for now."
 * According to the TV Anime 108 Fanbook:
 * Guren's favorite color is blueish-gray (or gray with a hint of blue), he said there's no particular reason for it.
 * He loves cola.
 * If he were to become a demon, he believes his demon form would appear at about five years old, the age when he first met Mahiru Hīragi and felt like he could do anything until the Hīragi retainers tore them apart and crushed his hopes and dreams.
 * He resurrected his dead friends by using the Seraph of the End experiment using their severed heads and bodies.
 * Guren is the only person who wields two demons at the same time.