Guren Ichinose

Guren Ichinose 「一瀬グレン, Ichinose Guren」 is the main protagonist of the prequel story Seraph of the End: Guren Ichinose: Catastrophe at Sixteen light novel series. Further more, he is an important character who plays a crucial role within the sequel story Seraph of the End: Vampire Reign manga series that takes place eight years later.

With the death of his father, Guren has since been the current head of the Ichinose family, when he was still 16 until present time 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. From teen to adulthood, he is also the squad leader of the Guren Squad.

Appearance
Guren is a tall, young man with medium length black hair parted in the middle and has purple eyes. He would sometimes have his hair slicked back even during the midst of a skirmish on the battlefield.

He wears the standard JIDA uniform which mainly consists of a long-sleeved black coat with red details including the shoulder epaulettes, and aiguillette that are decorated for it. They're worn on the right shoulder with a five-pointed star decoration, and two rows of gold buttons on the front. Along with that, he wears a pair of white gloves, an armband on his left arm, and a white web belt with 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's illustration, he also wore a cloak with an outer layer that is black while the inner layer being red. Whereas in the anime's artwork instead, the cloak is purely maroon from both inside and outside. Despite differences of the cloak's appearance for either manga or anime, what they do have in common are shoulder epaulettes with a golden emblem implanted on it and a symbol by the side of the cloak's neck. To add on, while shoulder epaulettes are primarily red in the anime, it is a mixture between black and beige in color pattern for the manga.

On the other hand, the cloak's appearance from which the anime depicted it to have are extra red markings and yellow details spread all around in lines too. In contrast to the anime, the manga depicted the cloak to have beige for its symbol and details too spread all around line by line without no markings visible.

Personality
Guren was naive in his childhood days and spent most of his time with Mahiru. His aspects on life felt simple as he was in his happy moments. But after he was treated with disgust due to his name as a lowly born branch member, he began to feel guilt. He thought that because of his weak physique and power, he couldn't reach out for what he wanted, which was hinted to be Mahiru. She motivated him to become stronger and wiser.

He later became a wise leader who values teamwork and cooperation, determined to ensure the survival of the human race from demons and vampires. When Yu tried to join the Moon Demon Company, Guren refused to allow him to join until he made friends.

Guren would sometimes pretend to be lazy, but in truth, he really works hard and keeps many secrets to himself, which he has no difficulty lying about. He also plans to dethrone the Hīragi Family and it was further explicitly desired by him upon being possessed by Mahiru-no-Yo. It was made certain from the fact when Guren is possessed, his true desires come to light that he wanted to change the status quo and hierarchy with Shinya.

In addition, he actually cares a lot about his subordinates and friends, considering them to be his family before and after the apocalypse started. It was the reason for why he haven't been completely honest with his squad whenever they're around him especially hiding from them about his second personality, which Kureto knew of and later Shinya. More so, it was another reason for why Guren's weaker, original personality have yet to be fully taken over by his second personality and continues to exist. Nevertheless, he has since kept his own emotions in check on a daily basis carefully when maintaining a positive image so not to worried them.

However, Guren's personality changes drastically when he's overtaken by his demon blade, Mahiru-no-Yo. According to Ferid, it happens more often than shown. Guren is described as being a Namanari, a human with two souls in his body, and is a single step away from closely becoming a complete demon. When Mahiru's in control of Guren's body, he becomes utterly ruthless in the pursuit of his goals and cuts down anyone who opposes him, especially one of his comrades like Shihō or Yu. He doesn’t distinguished the vampires or humans as neither a friend nor foe to him in his view, but a sacrificial pawn for the “Seraph of the End” experiment.

History
Guren was born into the Ichinose family and is a member of the Mikado no Tsuki, a low branch of the Hīragi family and Mikado no Oni. He was also the best friend and lover of Mahiru Hīragi, but this was frowned upon by the higher-up officials because of his low birth or social status. Since they were friends, Guren was treated badly and blamed for becoming too close to her. As a result, it was the reason for him to receive a lot of harsh beatings by the adults from the high-up at an early age during his childhood. Despite the bad treatment towards him and the Ichinose family, this has only motivated Guren to train harder and grow stronger while growing up with a new sense of determination. Moreover, he volunteer to become a subject of a Kiju experiment for the sake of his family and obtaining an advantage over the Hiragi family. At the age of 16, he was later befriended by Shinya Hīragi, Mito Jūjō, and Norito Goshi alongside his retainers, Sayuri Hanayori and Shigure Yukimi. From this moment forward, they would come together and form a new squad under Guren's leadership in carrying out missions.

Mahiru was stated to have been the primary cause for Guren to actually turn into a Namanari that is part human and part demon while retaining some form of humanity left in him somewhere during around his lifetime. This was shown when he initially became an Oni in the first place because of her direct action as a demon herself, which created a sinister nature to bear fruit from inside Guren's morality be born. It has also deeply affected his mental way of thinking and physical action as well for those who're around him that he want to see be kill or by his own hand. To further add on, Guren have chosen to lose his humanity the moment when he has made a contract with a powerful demon called Noya for the first time. Accepting its power, this was also Guren's first demon weapon from the Black Demon Series prior to wielding Mahiru-no-Yo, another of that same ranking. According to Shinoa, Guren was the one who had finally put an end to his lover, Mahiru by killing her, but in vain, made it a demon weapon for him to use eight years later in the sequel.

Guren appeared at the end of chapter 1, using information from a prophecy to collect Yūichirō Hyakuya, a survivor of the Hyakuya orphanage. Along the way, later on, he has also found two other survivors, Shihō Kimizuki and Yoichi Saotome. Later, it is revealed that these humans are actually the seraphs he secretly collected and sought after during the Hyakuya's downfall. Guren has led Yūichirō to join the Japanese Imperial Demon Army after the moment he has escaped the city of vampire. Meanwhile, Guren seems to be secretly attempting to reform the Japanese Imperial Demon Army governed by the Hīragi family and is having an internal power struggle while fighting with the higher-ups stated by Mitsuba. Besides Mahiru, he has also help developed the completion of Cursed Gear weapons. Secretively, at some point in his lifetime, Guren have been in cahoots with the seventh progenitor, Ferid Bathory. As the two meet up in an isolated area, they would then share and leak out valuable information from both the enemy's respective organizations to one another for the sake of reaping it to their own benefits.

Four years earlier in the manga, Guren had since look after Yūichirō as a guardian and mental life support, keeping a close watch over him before he made any friends. Whenever Yūichirō has trouble sleeping because of a nightmare from his past experience, Guren would go and check up on him, making sure if he is feeling alright. This was while at the same time, offering Yūichirō advice on how to live from now on, giving him a more meaningful reason to live even if it is to exact revenge against the vampires for the death of his family. Since then, Guren have taken Yūichirō under his wing, raising him as a capable swordsman of his own right through training. On the other hand, he is rumored to have even accomplished, recapturing Shinjuku from the vampires with a single team at some point in history.

Volume 1
The English omnibus with volumes 1 and 2 comes out January 26th! Be sure to buy them!

Volume 2
The English omnibus with volumes 1 and 2 comes out January 26th! Be sure to buy them!

Volume 3
Iori Mitsuki draws blood from Guren’s arm and reveals he has an unknown man-made poison in his blood with curses mixed into it, thanks to Mahiru. They discuss human experimentation, and she rashly injects Guren’s tainted blood into herself. When her left hand transforms into a demon’s, Guren severs it. The hand continues growing and attempts to devour Mitsuki, but Guren kills it. He tells the researchers that any research must be completed by Christmas.

Rumors about Guren hiding his strength flood the school. During class, Shinya passes a note to Guren revealing that the Hyakuya Sect is planning to meet at 2:00 a.m. the following morning at the tennis courts in Hikarigaoka Park. Guren carefully pockets the note while being sure to preserve Shinya’s fingerprints.

Kureto calls Guren right after class and orders him to go to the student council room during lunch the next day.

Guren, Shinya, Mito, and Goshi play shogi in an elimination-style tournament after inviting themselves to Guren’s apartment, and Shinya realizes Guren lost to Goshi on purpose. Meanwhile, the 6 p.m. news plays a broadcast about a fire going on in a condominium. A mad woman screams about a demon and says no one must put out the fire. She then lights herself on fire. Saito from the Hyakuya Sect approaches the camera, and the footage ends.

The group leaves, and Shinya sneaks back to discuss the fire with Guren. He says they need more information before doing anything. There are no additional news reports on the fire, suggesting that the Hyakuya Sect censored them.

Guren arrives at Hikarigaoka Park at 1:30 a.m. the next morning, shortly before Shinya. They sneak into the park and see a common vampire easily slaughter eight trained Hyakuya Sect members before turning her attention to them. They flee, but she crushes the tire of Guren’s stolen motorcycle. While fending her off, he rides behind Shinya on the other stolen motorcycle and run wild at high speeds throughout the city until she eventually decides they are not worth her effort and lets them go.

He finally returns to his apartment after a few hours, and Shigure and Sayuri panic about a wound on his forehead, and he is concerned his blood could taint them. Guren finally collapses into bed at 4 a.m. but cannot 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, and Kureto begins asking him about Mahiru. Guren denies knowing anything. Eventually, Kureto reveals that all of this is makeup, and he did not actually torture Shinoa. Kureto holds Shinoa by the neck and threatens to break it when Guren attacks him.

Mahiru sends Kureto a message telling him to do as he pleases, and tears briefly form in Shinoa’s eyes. Kureto orders Guren to either hold onto Mahiru or kill her, and he says he will permit them to marry because he wants to keep her in the family. Kureto states she is stronger than him. Kureto sends the IP address to Guren, and Guren sends a message to Mahiru.

Mahiru calls Guren, and Guren puts the phone on speaker. Guren, Shinoa, and Kureto all speak to her. Mahiru twists the conversation and repeatedly states that all of the events occuring since the first Catastrophe volume are his doing. She reveals the special ops he sent after her just now are already dead. A student rushes in and reveals that this entire conversation was just broadcasted over the whole school.

Today’s date is August 21st.

Kureto releases them.

Mahiru calls Guren again, stating she only wants to hear his voice and says the demon was in control before. They establish a rendezvous 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.

Although she tells Guren he cannot save her, he insists he can, and they have sex that evening. She tells Guren that he wants to protect his own comrades rather than her. Mahiru reveals she now has both her demon and Shinoa’s demon inside her body, which has sped up the rate of her degeneration. She shared part of the demon with Guren before in order to remove all of the demon from Shinoa, so he will eventually become a demon as well. When he asks to fight by her side, she tells him there is not enough time and reveals the Apocalypse occurring that Christmas.

The vampire from the previous night comes through the balcony and greets Mahiru, but Mahiru calls upon Asuramaru and quickly kills her.

Mahiru reveals she fabricated information to set the Hiragi House and Hyakuya Sect against each other. Guren says he refuses to let her give up her humanity. Mahiru jumps out the window. Sayuri and then Mito call Guren and report that the Hyakuya Sect is attacking the school, but his phone disconnects. Cursing, Guren leaves and comes across a running motorcycle and a demonic sword waiting for him in an alley.

Guren calls Kureto and reports what happened. He asks Kureto to kill him if he loses control during this experiment. He then calls Shinya and reports that he had sex with Mahiru, and he tells Shinya that he will leave Mahiru to him if he dies. When Shinya asks if Guren wants him to marry her or kill her, Guren hangs up.

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

Volume 4
Guren contemplates what to do in the face of imminent failure and decides to fight to fulfill his ambitions at the risk of losing everything. The prologue picks up where he grips the demon sword Noya.

Guren hears Noya calling his name and converses with him in his heart. Willingly giving up his humanity, Guren accepts the demon. Noya says it is unacceptable for a human to give up his humanity while he is still human. The power overwhelms Guren, and his vision goes black.

Guren wakes up with the sword in his hand and the motorcycle next to him. He hears the war going on around him, but he only feels the desire to kill. He mutters about needing a sheath to surprises the demon’s will before getting onto the motorcycle and heading to school.

Guren goes to the battlefield at the school and kills many Hyakuya Sect members, but Noya is the one mostly in control. Noya makes him kiss Mito and grow horns, fangs, and claws.

Mito and Goshi narrowly escape while Mikado no Oni 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.

Mito, Shinya, and Goshi play video games at Guren’s apartment until Mahiru shows up. Guren attacks her, and they fall from the twenty-fifth floor. Mahiru stops her fall by using her sword. Guren is badly injured but recovers.

Volume 5
Guren and Shinya play Bomberman until 3 a.m., and Mito and Goshi are already asleep.

Another day, Shiny and Guren visit Shinoa at her apartment sitting in the dark with nothing but convenience store food to eat. 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 Mikado no Oni, 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 throws a knife with an exploding tag at Guren’s face, but he catches it.

Later, Guren leaves Shinoa behind to keep her safe while he returns to his apartment. He plans his next move with his group and reveals some documents Mahiru left to him about the Seraph of the End.

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 Mikado no Tsuki. 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 and head down to a farmland to steal a tractor. Guren sleeps for seven hours while chatting with Noya. They return to a love hotel and change clothes.

While there, a vampire appears, but they kill her. Asuramaru’s sword materializes in the room.

Volume 6
The prologue shows Guren and Mahiru’s first meeting when they were five years old. Guren is training late and night and jumps into a river to cool off. Mahiru appears and claims to be a forest fairy, but Guren points out that they are in the mountains. She reveals that the Ichinose are the reason her mother died.

Guren has a final meeting with Sakae before his execution. Despite Kureto’s objection, the council heads overrule him and decide to execute Sakae for his arrogance. Sakae tries to have them part with a smile.

When Guren looks at his father’s corpse, Noya tempts him, but Guren manages to resist. Shinya calls and offers to clean up Sakae’s body, but Guren asks him to come to his apartment and play games instead.

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. Makoto Narumi and Shusaku Iwasaki ask Guren if Mikado no Tsuki will be treated like this for the rest of their lives, and Guren tells them to endure it and support him for now.

Guren reports to the Hiragi headquarters, where Tenri Hiragi forces him to kneel before him while he stomps on Guren’s head enough to make it bleed. He says he forced Sakae to dance naked.

After Guren is dismissed, he returns to his apartment to see Saito lounging on his sofa. They fight, and Guren accidentally cuts off Shigure’s arm. Saito reveals he is actually a second progenitor who has been alive for over 1000 years. He asks Guren to kill his servants and join him.

Guren calls Kureto, who sends in a helicopter. Shinya calls Guren, stating he bugged Guren’s room, and Guren says he accidentally chopped off Shigure’s arm while trying to cut a radish. They meet at Guren’s apartment that night, and Guren informs Kureto about Saito. Shigure’s arm is successfully reattached.

When Guren heads home, Seishiro attacks him with a group of underlings, but Guren defeats them. Shinya saves Seishiro and convinces him to leave Guren alone. At the apartment, Guren finds Mito and Goshi eating curry. They play Bomberman.

On December 10th, Kureto sends in Guren and his gang to take care of students that have become possessed by demons at the school. Guren arrives first and knocks out one demon-possessed boy. Mahiru, now a vampire, appears and applauds Guren’s strength. She admits this was her doing and asks about the experimentation on Asuramaru. She says a human must be modified in order to use a Black Demon, but the current success rate is less than 20%. Guren says he wants to protect both her and his friends and asks that she surrender, so he can extract the demon from her. She throws down Shikama Doji and instructs him to give it to Shinoa in order to protect her. The rest of the group arrive and attack Mahiru, but she escapes.

On December 11th, Mito confesses her feelings to Guren, but he rejects them.

On December 23rd, Guren investigates the abandoned Hyakuya Orphanage in Shibuya. Although reports from the Nii and Kuki families say the children have been killed, it appears they were alive recently. Mika’s diary is dated for December 18th. Guren informs Kureto, who realizes the Nii and Kuki families are traitors.

Guren takes Shikama Doji and gives her to Shinoa, but Shinoa loses consciousness. The traitors attack them, but Guren escapes with Shinoa. Goshi calls Guren and says his apartment was set on fire by traitors. The call is dropped. Guren steals a bike and escapes, but a van chases him until Shinya uses Byakkomaru to destroy it. None of Guren’s group die at the apartment. Goshi picks them up in a stolen minivan.

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

Prologue
Guren arrived outside the entrance of Sanguinem during the daytime at the end of chapter 1. 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 the beginning of chapter 2. 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 chapter 2, 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. At the end of chapter 4, Shinoa recommends both Yu and Kimizuki to Guren as candidates for the Black Demon Series weaponry. He plans to rebel against the main family.

In the following chapter, we see him 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.

In chapter 6, Guren appears in the classroom. Sayuri informs him that Yoichi may be stable enough to resist demonic temptation. Guren attacks the classroom, filling with a 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, 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. He says that sacrifices are necessary and scolds 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. He informs her that the drugs wear off after five days, so Yu should wake up soon.

In chapter 16, 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 demon 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, Mahiru. 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 whater 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
In chapter 23, Guren meets 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.

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 Yū had, and Yū 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 ever 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 in chapter 38. He is 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 in Chapter 40, 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
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 Hiragi and Guren Ichinose 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.

Whereas in the anime, four months have already pass right after the battle at the Nagoya airport ended in contrast to the manga with its three month timeskip and has yet to successfully take over Saguinem. It was during that time, however, in which Guren is still under the possession of Mahiru, who appears standing next to Kureto in the underground vampire city, Sanguinem that the JIDA has now taken control of it 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.

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.

He is an incredibly, skilled swordsman, strategist, and leader who can hold his own in a fight. This was shown when Guren is able to kill several common vampires with a single strike and almost come close to securing a fatal hit on Mikaela before Ferid came to his rescue. 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). Back when he was still a teenager, Kureto has regarded Guren's capability as being political in nature. As they've known each other at the span of about eight years, Guren was his right-hand man in carrying out his missions. Born with extreme talent in the Ichinose family, Guren was able to see through one of Goshi's illusionary techniques and anticipated Mito's Vajrayaksa Curse before easily countering it. At one time, he is able to have an even sword fight against Kureto though it was said by him that Guren was probably holding back.
 * Anime: While slashing each and every one of them with his sword, Guren can repelled 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 happen, it actually happen in the anime. Not sustaining any minimum damage from the two, Guren was able to fend off both of them at once simultaneously and then low-kicking Shihō away while handling Yūichirō on his own.

Guren is also adept with the prior 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 also specialized in other assets like the use of magic and spell tags, strategizing them as part of his battle plan. Moreover, he is quite analytical of the predicament around him, such as ordering the group to retreat. He would go so far as ordering Shinya to abandon him and take command for the group in his stead so they can escaped out alive while carrying on with their mission.

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 for the first time when they met before since he was 16 and later on in the battlefield as an adult.
 * 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. Due to his physical prowess being bestowed by the demon weapon, Mahiru-no-Yo, he can fight on par with Mikaela evenly, a true and complete vampire that wields a first-class vampire sword. Even though they manage to battle out each other as swordsmen of their caliber, moreover, he is still able to overwhelm Mikaela in terms of his physical strength and power. This was portrayed when Guren lift Mikaela by one of his foots, and then throwing him to Yūichirō, 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 he was still at his late teen. He can successfully implant one of these spell tags against 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. Guren uses one in particular like this to serve as a distraction in his battles against Yūichirō and Mikaela.
 * 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.
 * Light Novel: During his late teen at the age of 16, Guren can implement a talisman on a regular sword to augment the weapon's cursed power and ability. Upon doing so, his blade's color scheme will then be completely enveloped with blood-like crimson flame. As a result, from synchronizing the talisman with the blade, it created an explosion to unnaturally occur on the enemy's body for physical damage.

Equipment

 * Kujakumaru: This blade goes by the name of Kujakumaru and is wielded by Guren Ichinose at the age of 16. It was an heirloom that had been passed down from generations in the Ichinose House. 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 Hiiragi House'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 destroyed the enemy's body, causing it to have their flesh be torn apart and atomise.

Cursed Gear

 * Glen's_Demon_Possession.pngMahiru-no-Yo 「真昼ノ夜, lit. Midday's Night」: A possession-type demon weapon of the Black Demon series wielded by Guren Ichinose. In terms of the weapon's appearance and shape, the blade presumably takes on the form of a black katana with a glowing crimson, red streak that is outlined down in the middle portion of it. Further more, it increases Guren's physical abilities significantly and in addition, when calling upon her name, it also increases his own power tremendously. Other than its demon blade better known as Mahiru-no-Yo, Guren can invoke her real name, to possess him if he wishes to. This resulted in Mahiru's apparition enshrouding Guren with streaks of overwhelming flames around his arm and hand that held the demon weapon he is gripping on. While so, he would then go on and launch his first attack single-handedly with one slash aimed directly at the intended target, which is strong enough to engulf an explosion in the midst of its vicinity.
 * Additionally, Guren can utilize the power of the demon weapon for one 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. In the anime, further more, the gases have taken up the shape and form of his cursed gear weapon, Mahiru-no-Yo, which can be incorporated into combat particularly such as a sword slash that he did pull off against a mock battle with Shinoa, striking away at her Shikama Doji.
 * 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. Although in the anime opening of Owari no Seraph: Nagoya Kessen-hen, where he had a standoff against Mikaela, the crimson-like, black demonic auras were summoned onto the demon weapon wielded by Guren, shining the blade with bright redness before quickly turning dark. The crimson-like, black demonic auras encompasses Guren with various streaks and sparks all around him in vast quantity.
 * Once Guren is possessed by his demon weapon, 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 launch at targets through him upfront 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 afar and outside while being put to a standstill for a moment temporarily.
 * In contrast to the manga, when Guren spoke of drinking the blood of human sacrifices, demons, and the progenitor, 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 all blade length such as how the cover for volume 8 was depicting its manga illustration upon further analysis. Likewise, the transformation of his demon sword's color scheme is exactly similar to how the first-class vampire weapons used by the progenitors drank their blood, giving shade to red as well. Not only that, something similar occured 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 the Black Demon Series into fully red without placing any sort of talisman on it.


 * Noya 「ノ夜, lit. ???」 is a demon who forms a contract with Guren Ichinose in Seraph of the End: Guren Ichinose's Catastrophe at 16 and becomes his demon weapon. He can call upon Noya to be sent flying back to his hand whenever they're separated. With the recent revelation from Volume 6, Noya is consider to be a powerful demon in the ranking under Black Demon Series. Like Mahiru-no-yo, Noya is also a possession-type demon too.
 * It seems the weapon is mainly concentrated on enhancing Guren's physical feats similar to Mahiru-no-Yo, and can become increasingly stronger the more he desires something.

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.
 * There was already a demon inside Guren's heart before he even made a contract with Noya. To be exact, Guren has two demons with him like Mahiru.
 * According to fanbook 8.5:
 * 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 fan book 108:
 * Guren's favorite color is blueish-gray (Mahiru had long blueish-gray hair).

Light Novel

 * "To me, who was lowly born, she was the sun...."-- Guren about Mahiru. Volume 1, prologue.

Manga

 * "There he is. Just like the prophecy said. One of the lab rats from Hyakuya Laboratories, the company that destroyed Japan. Boy. You are going to be of use to me in exterminating vampires."--Guren to 12-year-old Yu after escaping Sanguinem, Chapter 1, "The World of Blood Legacy"
 * "Sorry, Kid. The army doesn't have use for virgins who are too scared to work in a team, make friends, or date. If you want in, then make a friend at that school and introduce them to me. I'm not holding my breath. YOU FAIL!"--A note from Guren to Yu, Chapter 2, "Humanity After the Fall"
 * "Quit screeching. Nobody wants to hear it, Vampire."--Guren to the escaped vampire, Chapter 2, "Humanity After the Fall"
 * "Nope. I hate brats who don't know what 'teamwork' means."--Guren rejecting Yūichirō from joining the Moon Demon Company, Chapter 2, "Humanity After the Fall"
 * "Okay, listen up. The reason that I, your homeroom teacher, decided to grace you all with my presence today is because we have two transfer students... Anyway, here they are. Yūichirō Hyakuya and Yoichi Saotome. They're the idiot and the crybaby, respectively. As of today, they're joining your class."--Guren to the Moon Demon Company classroom, Chapter 4, "The Worst Pair"
 * "Leave 'em. We won't get anything done in class with them conscious. Right then. The Cursed Gear aptitude test is coming up in a week. It's been a while, but I guess I'd better teach you guys something, eh?"--Guren to the Moon Demon Company classroom after pulverizing Yūichirō and Kimizuki, Chapter 4, "The Worst Pair"
 * "That doesn't matter. Strength alone is not enough. Make friends. Find companions. Don't try to handle everything by yourself. Because if you do... when the demon sinks its claws into you... it will swallow you whole, and you won't be able to come back. Anger and impatience are a demon's favorite snacks. As you are now... you'd be devoured by your own desires and turn into a demon yourself."--Guren to Kimizuki, Chapter 4, "The Worst Pair"
 * "I guess it's time I started making some preparations to steal the throne of this little kingdom out from under the main family."--Guren to Shinoa, Chapter 4, "The Worst Pair"
 * "Oh, I most humbly beg your pardon, General Tenri Hīragi. It's just that I was bored out of my mind."--Guren to Tenri Hīragi, Chapter 5, "Vampire Mikaela"
 * "Ugh! Dealing with idiots can be so exhausting. Still... Things are about to get a little more interesting."--Guren to Tenri Hīragi, Chapter 5, "Vampire Mikaela"
 * "If you're not strong enough, you die. That's the way the world works now. We aren't holding hands and playing house here."--Guren to Sayuri, Chapter 6, "Black Asuramaru"
 * "Well, damn. I guess Yoichi wasn't quite strong enough after all. Still... A two-out-of-three success rate with the Black Demon Series is pretty good."--Guren to Yūichirō and co., Chapter 6, "Black Asuramaru"
 * Okay, you two have your Cursed Gear now, so here's your first official Moon Demon Company mission. Yūichirō. Kimizuki. Look at the ceiling. There's a man-eating demon up there. You two go kill it."--Guren to Yu and Kimizuki, ordering them to kill Yoichi, Chapter 6, "Black Asuramaru"
 * "YOICHI! Are you going to hide underneath that bed and watch your family die again?! Get out of here and protect them!"--Guren to a possessed Yoichi, Chapter 7, "New Family"
 * "You have talent. But you feel guilty because you couldn't save your sister. That's sapping your desire to live. But today... you've found enough reason. Your reason to live now... is to protect the ones who saved you today. Your friends. Revenge? Don't let something so petty consume you. That goes for you too, Moron. Forget your old family. Because you have a new family now. Put your life on the line for the ones you see before you. The past is gone. There is only the future."--Guren to Yoichi, Yu, and Kimizuki, Chapter 7, "New Family"
 * "Sheesh. Raising kids is exhausting."--Guren to himself, Chapter 7, "New Family"
 * "Oops. I missed their commander. Ah well. Once we control this point, we'll have have won anyway. Hey, Vampires! Was all that human blood you drank today tasty? Sure hope so... because that was your last supper. Here we go. Give me more power, Demon Blade: 'Mahiru-no-Yo.'"Guren's pre-battle speech, Chapter 11, "Queen's Contract"
 * "Oh ho! You're a strong one!"--Guren to Mikaela Hyakuya, Chapter 12, "A Very Safe Supplement"
 * "Over here. Checkmate, Vampire."--Guren to Mikaela Hyakuya after trapping him, Chapter 12, "A Very Safe Supplement"
 * "Thanks for your patience. Mind if I ask you to wait just a bit longer, though? It's time for us to take our medicine, see. Do you mind giving us, oh... another 20 seconds or so?"--Guren to Mikaela Hyakuya after reevaluating Mika and Ferid's strength, Chapter 12, "A Very Safe Supplement"
 * "So then, if I told you we're using him in our experiments, would you be angry? Humans are weak. Fragile. Now that the world has ended, what do we have to do to survive? What do we have to do to kill vampires? To eradicate the horsemen? Your sister, Mahiru Hīragi, invented Cursed Gear. How many people were sacrificed in that long process? Without it... do you honestly think humanity would be able to survive? Understand? So quit spewing idealistic crap at me, Little Girl. Or, what... Are you falling in love with Yūichirō?"--Guren to Shinoa about Yūichirō, Chapter 14, "Everyone's a Sinner"
 * "Yūichirō. You remember, right? Who the one who saved you was. Me. Don't forget who was there for you when you came crawling out of the vampire capital. Me. I went out of my way to teach you how to live here. Even how to use a sword. If you feel like you owe me at all, then pay me back today. You live because of me. You are mine. You belong... to my faction. So don't go wagging your mutt tail to the Hīragi."--Guren to Yu, Chapter 16, "Human World"
 * "You're wrong about one thing, though. I'm not your friend. [I am] your superior. The guy you owe your life to. Your surrogate father. Put all those together, and I'm practically a god to you. You can even call me 'papa' if you want."--Guren to Yu, Chapter 16, "Human World"
 * "Sheesh. Did you have to go on a stupid rant about the obvious, you idiot? I already told you... Everyone standing here right now is family. That includes me. Family... works together to bring back family."--Guren to Yu and their squad about Mika, Chapter 18, "Possessed by Mahiru"
 * "So now is the part where you show off your special hostage? Who is it this time? Are you going to torture Shigure, Sayuri, or any of my other aides in front of me?"--Guren to Kureto, Chapter 23, "Ambition in the Demon Army"
 * "Shaddap. I'm not that dumb. I'm scared of who I could lose on this mission. But... we have to answer the call. If we fail, humanity dies. And so, Shinya. Goshi. Mito. Sayuri. Shigure. I want to complete this mission with as few casualties as possible. For that, I ask for your help."--Guren to his squad and Shinya, Chapter 24, "The Moon Demon's Orders"
 * "SHUT YOUR MOUTH, CHILD! This mission is not a game!! If you can't follow even basic regulations, we don't need you! Go home!"--Guren to Shinoa in front of the Moon Demon Company when her squad arrives late, Chapter 24, "The Moon Demon's Orders"
 * "Listen up, everyone. During this mission, I will have zero tolerance for anyone who doesn't follow regulations. Nor will I tolerate anyone treating this like a game or messing around. I repeat, this is not a game. This is the most difficult, dangerous mission we have ever undertaken. Some of us are going to die. We are all family here. And on this mission, we are going to lose a lot of family members. But despite that danger, this is a mission worth risking our lives for! Listen up!! I don't want us just coming home alive... We will come home victorious!! DO YOU HEAR ME?!"--Guren to the Moon Demon Company, Chapter 24, "The Moon Demon's Orders"
 * "It's your punishment. Shinoa. This is your squad. I'm doing you a favor and teaching you that even a little mistake could kill them.... You don't get it. You've never had anyone important to you before. You don't know what it's like to fear losing someone. But now things are different. Even a tiny mistake is enough to kill. Your little pranks could cost your family their lives."--Guren to Shinoa, Chapter 25, "Narumi & The 20-Year-Old Yu"
 * "You have three Black Demon wielders on our team. What the hell was that? You showed very little teamwork. The vampire nobles we'll be facing are stronger than us three. How do you expect to fight them? Or do you plan on standing there, cracking snarky jokes while you die?"--Guren to Shinoa's squad, Chapter 26, "Thirst Logic"
 * "We're going to reinforce Shinoa Squad and Narumi Squad. Once we do that, I'm adding a new target to our list. He's currently located in the Nagoya City Hall. We are going to kill... Thirteenth Progenitor Crowley Eusford."--Guren to his squad, Chapter 28, "Livestock Revolt"
 * "Anyone with a heart cries when a friend dies. But we can't afford to do that right now. We have a mission to complete."--Guren to Shinya, Chapter 29, "Who's Pulling the Strings?"
 * "You idiots!! Why the hell did you come?!  Follow your orders, dammit!!  Get out of here now!!"--Guren to Shinoa Squad, Chapter 33, "Demon's Lullaby"
 * "I'm already done for... Save your strength for getting Shinya and the others out of here."--Guren to Norito Goshi, Guren Squad, and Shinoa Squad, Chapter 33, "Demon's Lullaby"
 * "Don't give up--Don't let the fear win. There's still a chance to pull out of this.  Vampires don't kill off their livestock all willy-nilly.  Make a little show of resistance...  Then talk.  Just give them a little dribble of info to lead them to Shinjuku tonight... and Kureto should handle the rest."--Guren's thoughts, Chapter 38, "The Namanari Awakens"
 * "Ugh.. Dammit, that hurt.  When did getting beat up get so exhausting?  Still, I should probably let him hit me a bit more to make what I tell him seem more convincing."--Guren's thoughts, Chapter 38, "The Namanari Awakens"
 * "Get your disgusting hands off of me, Bloodsucker. Touch me again and die."--Demonic Guren, Chapter 38, "The Namanari Awakens"
 * "At Nagoya Airport, I am going to conduct an experiment on the Seraph of the End. You will assist me, Vampire."--Demonic Guren to Krul Tepes, Chapter 38, "The Namanari Awakens"
 * "Mahiru is dead. I couldn't save her."--Guren to Krul, Chapter 39, "The Beginning of the Plan"
 * "Then, kill me. Go on.  You can't, can you?  You've betrayed your own kind too deeply to turn back now.  You, too... have to make sure the Seraph of the End experiment succeeds....  Today."--Guren to Krul, Chapter 39, "The Beginning of the Plan"
 * "Ung...! Ha... ha ha...  Ha ha ha!  Yes, that's it!  Keep up the act... Krul Tepes!!"--Guren to Krul, Chapter 39, "The Beginning of the Plan"
 * "Hello, Yu."--Guren right before betraying Yu, Chapter 40, "Trumpet of the Apocalypse"
 * "Drink the blood of the sacrificial humans... The blood of the demons...  The blood of the progenitors...  Drink the seraph of the end."--Guren during the experiment in Nagoya, Chapter 40, "Trumpet of the Apocalypse"
 * "Hold still, Child. We have not yet offered enough blood to control the seraph."--Guren after stabbing Shiho Kimizuki, Chapter 40, "Trumpet of the Apocalypse"
 * "What? Why stop?  Kill me, you little wuss."--Guren to Yu when Yu hesitates to kill him, Chapter 40, "Trumpet of the Apocalypse"
 * "No, not yet. Guren.  Sleep.  Do not wake up yet.  If you wake up into this, you will be scarred for the rest of your life...  Ha...  Ha ha...  Yes...  Everyone is a sacrifice..."--Guren to himself after seriously wounding Yu, Chapter 40, "Trumpet of the Apocalypse"
 * "Do it, Yu. Break their taboos.  Only someone so arrogant who desires to be loved by everyone...  Only you can do it."--Possessed Guren encouraging Yu to fall from an angel and become a demon, Chapter 41, "Arrogant Love"