Mahiru-no-Yo

Mahiru-no-Yo (真昼ノ夜) is a possession-type demon of the Black Demon Series. A merged entity from the Seraph of the End series, this being is a fusion of Mahiru Hīragi as a vampire and the demon Noya. When Mahiru stabbed herself with a sword containing Noya, she was soaked in the curse while he became silent as they became the same Cursed Gear. As a sword, they would be wielded by Guren Ichinose, where being a demon inhabiting the weapon and a human host they heavily affected his personality. Also guiding his actions, Mahiru-no-Yo had and could communicate their own goals, which largely involved Guren adhering to their direction.

Also fine with Guren drawing upon power to further his own transformation into a demon, they enabled their wielder the enhanced physical capabilities to be able to stand against supernaturally powerful vampires among other strong foes. Malicious energies from them emitted from the sword could also be used for ranged assaults. Unlike other demons, Mahiru-no-Yo acted on capabilities to leave the weapon, and is willing to perform as a scout.

Observational in their viewings, Mahiru-no-Yo would express familiarity with people who the Mahiru aspect knew. While generally silent otherwise, Mahiru-no-Yo can appear unemotional of those she regards, due to their distant nature in general. When the time came, they eased Guren into accepting his role to betray everyone. Stabbed through the chest by Guren, they would be split into their component parts, namely Mahiru and Noya with their distinct traits intact.

Appearance
Outwardly they appear exactly as Mahiru with the exception of having fangs and red eyes due to having been a vampire when turned. They are the only demon who does not have pointed ears or horns at all unlike others. At a later date, Mahiru as a singular demon would show the capability of producing long relatively thin cone like horns, where it stands to reason that Mahiru-no-Yo may have been able to reveal such a display if desired. From Mahiru's clothing as she passed, they still wear the female First Shibuya High School uniform, a sailor fuku.

In their sword form, they appear as a long black katana with a glowing crimson, red streak that is outlined down in the middle portion of the blade. The dark colored, purple-tinged handle has an almost golden colored guard between it and the blade. When powers are generated to benefit Guren, it is the handle area that is often enveloped.

Anime: Mahiru-no-Yo is portrayed to have a more saturated hair color, and the size of her breasts are toned down more.

Personality
Merged with the demon it was essentially Mahiru's appearance on the outside, with a possession-type demon within, where the status alone suggests that they are particularly violent. They are patient in helping Guren grow into a namanari, and possess him as needed to make his demonic side take control. Equally possible it is due to playing a long game, or because demon and human personalities are balanced, Mahiru-no-Yo does not appear to be as twisted as when Mahiru used to be as a namanari. Able to make calm and rational decisions, the being displays a purported love for Guren and Shinoa. It is warped though as they seek to turn Guren into a demon. Presenting a softer side towards Guren, they took time to comfort him genuinely when he was about to become a demon over his pensive guilt of causing the Catastrophe. Even taking responsibility for it along with him, Mahiru-no-Yo effectively expressed a solemn tone while Guren dwelled on his regret over being unable to save Mahiru. They were soothing in easing Guren into embracing his transformation. Where concern for Shinoa's wellbeing is shown, Mahiru-no-Yo is hoping her love will awaken her demon too so that she can become stronger. Where as a vampire Mahiru indulged in grisly acts of violence, and being a human to begin with willing to embrace violence while smiling, Mahiru-no-Yo's lack of viciousness does not seem to stem from inner kindness on Mahiru's side, but a tranquil contentedness that her host will fall.

History
Very unlikely to have been done without the outcome considered, the knowledge was likely there at the time that a vampire could be fused with a demon to become the same force inside a weapon. Where Guren had a previous demon, Noya, when he threw the weapon away, Mahiru picked up the sword and stabbed herself with it in the heart. Merging with it was what Mahiru had planned all along. For his part, Noya was unable to stop the curse from spreading to her and eventually Mahiru was sealed with Noya thus transforming them both into Mahiru-no-Yo. History may have been made with this union, where they became the demon within Guren's Cursed Gear and part of the Black Demon Series. This would take place before the catastrophe, where Mahiru-no-Yo was ready to be used for the challenges to come.

Events of 2015
At first Guren had no idea what is contained in his sword, if it was Noya or Mahiru. While he knew that Mahiru did absorb Noya, he remains unsure. In any case, Mahiru-no-Yo's demon power can be felt by Guren in his sword, which is mentioned as stronger than before. A bystander of sorts, Mahiru-no-Yo makes no reaction to Guren's lies to his friends about Mahiru's disappearance. In Guren's dream, Mahiru sat across the river on the opposite bank. A smiling Mahiru glared at Guren in silence as he and his friends were having fun. It is often the case that demons would tap into, and exploit strong feelings to wear down the human they would like to posses.

After Guren wakes up, and Kureto's long interrogations, Mahiru-no-Yo's essence is picked up on when Kureto tells Guren the demon inside him has advanced to a stage beyond their current technology. When Guren demands to know if Mahiru is inside him, Kureto denies it by saying only a demon lives inside. Kureto finally tells him that he is been hallucinating much to Guren's confusion. With it explained his dream is due to his demon making him hallucinate what he wants to see, Guren denies this but Kureto says this is the result of their readings.

Later Guren lies to Kureto that he already killed Mahiru and she disappeared into him which was his last memory in the underground lab. Kureto explains that he drugged Guren and found out that his demon is out of control to the point that his levels are off the chart, but yet he remains totally sane. He thinks that Mahiru did this to him. With the interrogation ongoing, Guren asks Kureto what is going inside his body. With the same answer, Guren questions why can he not hear his demon voice, but Kureto moves to explain the development of a drug to bring demons under their control, specifically suppress them.

There is no response from Mahiru-no-Yo when Guren tries calling out to his demon by invoking Noya to no avail. Their presence is still seemingly felt though since Guren still feels his demon supplied him with power. Further, Kureto was surprised by Guren's demon power when their swords clashed. The blade is sheathed by Guren after their brief clash. Later Kureto produces a syringe to use it to talk to his demon, and finds out that Guren's hand are resisting the drug. Though Kureto resorts to force the injection inject him, while he struggled and mentions it is not working, when the drug finally begins to work, Guren apologizes for the trouble. When Raimeiki states to Kureto that it is not Guren, the Guren silences Raimeiki. Questioned by Kureto if he is the demon or is he Mahiru, it is revealed that Guren is possessed and conforms so.

Where there is demon influence, Kureto questions the possessed Guren several questions but he brushes them away. When he says he does not want to disappear, Kureto shuts up Mahiru and she laughs. Informed by Kureto about the drug that will bring their demons under their control, the possessed Guren laughs in the ridiculing of this statement. After Kureto tries to get a hold of Guren to bring him back, he conforms he is but suddenly has a bout of insane laughter, before Guren began clutching at his head and blacked out.

In Guren wondering if Mahiru is inside him, Kureto again says only a demon is inside. When Guren tries to talk to his demon Noya, finally a voice responded although Guren noticed the voice did not come from his mind but from the window in the classroom. As he saw Mahiru-no-Yo for the first time sitting on the windowsill, it was the case they were able to be seen only by himself as Kureto couldn't perceive the demon. While Guren lies to Kureto by saying that Noya did answer him, when Kureto asks him if he remembers what happened, Mahiru-no-Yo speaks to Guren from the window to tell Kureto the Imperial Demons had killed her and he did go berserk. Though Guren had doubts what was going on and he had no choice but to listen to her words.

In response to Kureto's series of questions, Mahiru-no-Yo's words are shared by Guren to him. The instructions from them were simply obeyed by Guren until Kureto becomes satisfied. Announcing the experiment is over and with the illusion in the classroom released, Mahiru-no-Yo speaks to Guren he should be glad since he trusted them, but they are ignored. Later, Mahiru-no-Yo was standing beside Shinya which made him hard to focus on with their chat. Telling Guren that they are real and to not be afraid, making a promise, Mahiru-no-Yo asks if he is glad that he said what they had told him say to because she knows Kureto more than him. Then going to sleep, Mahiru-no-Yo bids Guren good night and vanishes.

Later when Mito was talking to Guren, suddenly Mahiru-no-Yo talks to him in annoyance and with jealousy. Wondering if Guren would be with Mito from now on (as he was with Mahiru all these years), they are ignored by Guren. When Mito says she was fine with the idea of her never loving her, Mahiru-no-Yo becomes aggravated and abruptly tells him to to do what she wants, then raises if he has not hurt her enough already. Continued to be ignored, with Guren proceeding with his talk to Mito that they recently took the drug and couldn't think correctly, their face falls on his lap. Saying to Guren that they remember the time both of them did the same thing, Mahiru-no-Yo raises is the reason just that Mahiru was not precious to him.

Again with no attention, Mito asks if they did not take the drugs, and if he would sleep with her. Although Guren doesn't mind, Mahiru-no-Yo comes to consider if this is really what Guren thinks, that he didn't need her body in their days together. Although she simply just could not live without it, Mahiru-no-Yo's concerns are disregarded by Guren. When Shinya and Guren keep talking about the meaning of life, with a back and forth on whether life has a meaning, Mahiru-no-Yo presses Guren to give him a good answer, then goes on as she just wants to help him. Not believed, Mahiru-no-Yo is asked if they know the meaning of life by Guren, to which they confirm so. In telling him that the ones he resurrected, namely Shinya and the others, It is mentioned they only have ten years to live as well, yet Mahiru-no-Yo will tell him the way to save them.

Thought to be lying, and seen as simply a demon by Guren who is just trying to take control of him, they deny the statements are lies. With the potential for Guren to still be dancing in someone's tune, Mahiru-no-Yo then reminds him that there is a vampire headed their way. When Shinya was about to attack the vampire, they tell Guren to have Shinya hold his fire as he has business with the vampire.

Called by Guren who wants to know how to save Shinya and the others, Mahiru-no-Yo materializes beside Guren to accept his request. Mahiru-no-Yo says they have got a lot of work to do.

In the Meguro ward of Tokyo, near Gakugei University station, Mahiru-no-Yo speaks to Guren. Mentioning that he has no shame, Mahiru-no-Yo sees the evidence as Guren gets aroused even at times like these as he descends from the stairs headed towards the vampire. Asked for their meaning, Mahiru-no-Yo answers him with an example of how an existential would drive someone when they are near death. On whether Guren is going to die, Mahiru-no-Yo replies they will not allow it, yet it does not mitigate his concern.

Stating that there will not be a fight with the vampire, Mahiru-no-Yo mentions only speak to him for Shinya and the others' sake to save them. Asked about the vampire, Mahiru-no-Yo is clueless as they have never seen him before. When Guren wants to know his situation to have a discussion with a vampire that Mahiru-no-Yo herself does not know, they remark about a possibility that the vampire is a conduit to someone else. If he is simply passing by at a wrong time, in which case it would be a bad idea to talk to him.

After Guren finally arrives at the ground floor while the vampire awaits him outside, Mahiru-no-Yo's guidance is sought as he does not understand the situation, namely whether he should approach the vampire. Considering that Shinya is on the top floor, Mahiru-no-Yo already knows that he is ready to shoot the vampire. Questioned if killing the vampire would cause trouble, Mahiru-no-Yo does not know.

Also sharing that there will not be a problem if he sees him talking with the vampire, Mahiru-no-Yo lectures Guren that a vampire would care less if he finds out that Shinya and the others are resurrected. Additionally, it is posed to Guren if he does not mind that Shinya would be wiped out of existence. However, Mahiru-no-Yo hears Guren does mind so they say if he does so, he should better take care of it. Hearing he will, they are glad of it. After spotting the vampire, Guren hid behind the building wall. Placing his hand on his sword, Mahiru-no-yo remarks how Guren feels that he has to kill the vampire, and states it is his intense bloodlust. As he drew his sword, Mahiru-no-Yo hears it is their opportunity where they hold the same opinion as him.

After a chat with the vampire, Guren kept thinking to himself about the tragedy that happened in the underground lab. Wanting to avoid the truth that Mahiru killed all his friends, he hallucinates to himself that it was his doing with Mahiru manipulating him. Interrupting his thoughts, Mahiru-no-Yo says if it does matter if it's the truth, as either way it does not change what he has to do. Told not to read his thoughts, they deny doing so as he was speaking out aloud, thus heard everything.

Accordingly, from this point Guren will close his mind off of them, so Mahiru-no-Yo tells him do as he wishes though it will not change his hopes and dreams. For him to buy more time for Shinya and the others, as well as bring her back to life as well, in addition to bringing the world itself back to life, before they can continue, Guren shuts them up. Continuing their dialogue, Mahiru-no-Yo affirms what Guren really wants is to be freed from his guilt, which is his only his purpose in life. For his desire, Mahiru-no-Yo finally says the time has come to speak with the vampire.

Later when Guren was talking to Saitō and wants to know what he did to Mahiru, he blames him for turning her into a vampire. When Saitō informs him she isn't a vampire either, and Guren demands what he did to her, he answers exactly what she wanted; Mahiru swallowed a demon and went inside him. The Mahiru-no-Yo sword is then levelled at Saitō's throat, and when Guren questions again what he did to her, getting the same answer, it is that Mahiru herself wanted Guren to survive. With Guren confused by this, Saitō states Mahiru wanted to become his strength and support him from within (Mahiru-no-Yo) herself. When Saitō takes out a Sinful Key dagger out of his chest pocket, Mahiru-no-Yo materializes next to him. Although Mahiru-no-Yo is unable to be seen or heard by them, Saitō did mention he senses a presence. Their location asked about, Mahiru-no-Yo confirms they are present, but also says she wouldn't able to hear him. While Guren informs him that she is standing next to him, he expected as much. Asking what he will use the dagger for, not telling him as it is for him to know, instead Mahiru-no-Yo is asked. Suddenly, Saitō then pierces Mahiru-no-Yo's throat with the sinful key. Giving a short cry, then placing hands on their throat, they collapse to the ground. When Guren screams, demanding what did he do to them, Saitō simply says he hid something which is a sin.

Turning towards Guren to reassure him that they will encounter Saitō again after he departed, he also left a letter for Guren. The warning is for Guren not to look at them, since Shinya is with him as well, and he will notice. It is advised for Guren to acquire the letter without Shinya noticing.

By passing off Caek, Mahiru-no-Yo suddenly gives a comment to Guren that most of his desires are guilt. While they sounded disgusted, Mahiru-no-Yo was disregarded by Guren.

Talking again when Guren was about reach the letter Saitō left him which he put it in his pocket, Mahiru-no-Yo wonders if he is going to read it now, but is shunned. Regardless, Mahiru-no-Yo informs him that they are feeding off his desires to know the secret even as they speak. Saying that she loves Guren, a claim of happiness that they are inside him is made.

Much later, Mahiru-no-Yo materializes and wanting to speak with Guren, they ask if it ever occurred to him that sleeping with her is a punishment. The question confuses Guren, and they tell him it is a forbidden love, wishing to do it again. As his body only wants to ravage her, kill her, the response from Guren in return is she only exists inside his mind as a fantasy. One that is complied with, still, Guren believes that she is just a hallucination that was created by his demon, and Mahiru-no-Yo asserts that they are a demon. Questioning how is it even possible to sleep with a fantasy, they start to tease him, annoying Guren. Laughing, Mahiru-no-Yo is asked whether they are real. Interrupting, Mahiru-no-Yo mentions that they have already proven that by telling him a vampire was coming. While Guren thinks to himself about how demons work and their personality, they cut him off as this is his mistake. This leaves Guren annoyed as he thinks that they can read his thoughts.

Remarking that they cannot read Guren's thoughts, as he built a wall around his mind, Mahiru-no-Yo would share information with him if he would lower those walls. The idea denied, with Guren not wanting to be their puppet, they say it is the opposite. As they try to come closer, after Guren takes a step back in return they laugh and call him a scaredy-cat, but Guren informs her he can't be blamed for being scared of them, being a genius and all.

Wanting Guren to conquer his fear as humans can only become stronger if they face their fear, it is mentioned she did conquer her own, shedding away her humanity as well. Shooting back the same to him, when Guren says he is human, they laugh, more so when the claim is repeated. When Guren enquires about Saitō's words, Mahiru-no-Yo is clueless about it. As even their first encounter was prepared, Mahiru-no-Yo says everything was planned as everything was one hundred years ago. Keen on the idea that this makes them soulmates, while Guren does not find her comment funny, it does lead to him intending to lower his walls on his mind for a moment for information. Upon noticing Shinya's sudden arrival, Mahiru-no-Yo vanishes and then teases Guren in his mind.

A boy named Kuro Kuki and his friends who loathe the Ichinose clan, see Guren as one, and annoyed he challenges him outside of Guren's apartment in the outside barracks. In response, Mahiru-no-Yo then informs Guren in his head about his strength. Although Guren guesses so he can handle it, they think that Guren might lose. Asked if they would be on the same boat as giving up, Mahiru-no-Yo simply answers that they insanely love him. Becoming more aggressive when Kuro keeps on insulting Guren, their attitude changes for the worse. Wanting Guren to make the boy suffer instead, silenced, Mahiru-no-Yo then reminds him they represent his own desires.

Although Guren states he can control them, Mahiru-no-Yo doubts it. Proof is desired, namely in unsheathing the blade, and with Kuro as well demanding for Guren to draw his sword, Mahiru-no-Yo urges Guren to speed things up. Ignored completely and without the sword drawn, Mahiru-no-Yo is left confused. While Guren was in the middle of fighting the boy cleverly using traps, Mahiru-no-yo suddenly speaks to give a comment that it isn't nice, a remark that does not sway Guren.

After beating the boy who is harshly talked to by Guren, they suddenly appear by his side. Standing, commenting as well how good it would feel, Mahiru-no-Yo is delighted when Guren continues to scold Kuro. Taking to remind Guren how he cleverly dispelled the boy's trap in the most painful way possible, after Guren knew they would love such moments there is the reminder of how Mahiru used to fool, toy and tempt with him and Kureto. Laughing at Guren, they are clueless at girls' opinions.

Saying to Guren that they have got "onlookers enemies" watching them, in reference to his friends who were observing the whole fight, they suggest to Guren to give the audience what they want, only to be silenced. When Guren then lectures Kuro about his actions, Mahiru-no-Yo states the reason he fought unsheathed is because he wanted to give a speech, this is ignored by Guren. They keep on going to add that Guren simply wanted to prove his righteousness, still ignored, yet they continue that Guren probably had some feelings to make it easier for him to punish himself as he was unable to protect them. This annoys Guren, and ordered to shut up and go away, Mahiru-no-Yo proceeds to detail that doing something like that is not his fault which is probably what he wanted to hear. Resulting in Guren getting more annoyed, told to go away, Mahiru-no-Yo then returns to the sword within his sheathe.

When Ferid confronted Guren in his apartment, Mahiru-no-Yo appeared behind the vampire noble. Their presence noticed by Ferid, they say for Guren to kill him while he has the chance as he is an interference for their plan. Shouting at Guren to kill him, their words do not tilt Guren to the cause as he was yet unsure if he should kill him and listen to them. Interrupting his thoughts, Mahiru-no-Yo mentions it should be obvious for Guren to only trust them and not resist them.

Not heeded, Mahiru-no-Yo the sword flew to Guren's hands to galvanize him to kill Ferid. Part of their identification is given away when Guren warns Ferid that they are trying to kill him where 'Mahiru' is mentioned, of which the name is recognized. This is detailed further when Guren informs Ferid that the girl he knew is inside him, all the while they pressure Guren to kill him. Consequently, Guren's body started to move according to their will which he is unable to stop. For their action, it is seen by Ferid as Mahiru having betrayed Guren despite them sharing a common enemy (Saitō).

As the Mahiru-no-Yo sword started to move on its own accord in an effort to cut off Ferid's head, the strike is avoided. Also leaving Guren feeling weakened as his mind was being consumed by the word to kill only, in response to a last resort of telling Mahiru to stop this, Mahiru-no-Yo then calms Guren. Guiding him to sleep, Mahiru-no-Yo explains everything will be over when he wakes up. Knowing that they have started to possess Guren, in declining to cease their actions as both of them are the same person they succeed in inducing sleep in Guren.

Having successfully possessed Guren and taken over his body, Mahiru-no-Yo has even altered his voice to be a little feminine. Where Ferid finds this all interesting, as he finally about to clash with Mahiru, after simply saying that he will kill her, Mahiru-no-Yo talks to him how about Saitō feels about him. With Ferid surprised that finally someone understands him, since he hates his father, the conversation is suddenly interrupted when he is attacked by Guren. Having speed that not even Ferid could counter, the blade lunged straightforward twice as fast at his face.

Though Ferid managed to dodge it twice and attacks Guren, then punches his face, away from his sword, after Ferid crushed Guren's skull he wonders why did Mahiru come out and possess him. After his face heals, Mahiru-no-Yo answers to kill him. Wondering on whose orders, Mahiru-no-Yo could only laugh as it does not matter and they are not capable of killing him. Reminding him that he is in Shibuya, it doesn't matter to him as they will find out who Guren is, if they would alert everyone to attack him.

Laughing as this has nothing to do with them, being Guren's "pathetic" attachment, the sword then seemed to have a will on its own as it struck the bed to slice it in half. The wall is then cleaved. When the alarm made a sound that a vampire noble has infiltrated the barracks, with soldiers gathering, Mahiru-no-Yo alerts Ferid that this is the end for him. Sure that his confidence got the better of him, and warning Ferid that today is his death, they close in on him. Mahiru-no-Yo cannot prevent Ferid running away or deny his intent to die another day.

Second Shibuya High School Arc
When a vampire escapes the school grounds, Mahiru-no-Yo the sword is used by Guren to slay it of which the power caused the vampire to disintegrate. Later, when Kimizuki arrives in Guren's office and asks him if he can receive a demon weapon, Mahiru-no-Yo is used by Guren in a demonstration of cursed gear's power by allowing the demonic aura to fill his office. Later, when Guren arrives at the classroom, Mahiru-no-Yo's withering energies send most of the class tumbling to the floor, many of whom go unconscious without the willpower to withstand it. Their power does not inhibit Shinoa who can remain standing because of her immunity to all demons, and Yoichi is completely unaffected by the attack to the point where he does not even feel it. The power unleashed is also withstood by Yu and Kimizuki, though they tremble.

Shinjuku Arc
At the Shinjuku 5th Street intersection with an invasion on the city underway, Mahiru-no-Yo is used by Guren to slay several vampires before confronting Mika and Ferid. The weapon clashes with Mika's sword, however the capabilities that Mahiru-no-Yo affords to Guren do not stop him from being defeated by Mika in combat.

Post-Shinjuku Arc
Following a conversation Guren has with Shinoa, Mahiru-no-Yo is met by the former in his mind. They want him to seek more power. When Guren addresses her, Mahiru-no-Yo says they are glad that he came as they wanted to meet with him. When Guren challenges Yu to a fight to test him for the next step of mastering his demon, during the match, Mahiru-no-Yo is ordered by Guren to possess him and overwhelms him.

Following their small talk, Guren reveals their form during a fight with Yu. 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 with Mahiru-no-Yo at that range. When Guren calmly says he would let Shinoa kill him, Shinoa asks him if that is his way to atone for killing her sister. That Mahiru stabbed herself by Guren's previous demon is unknown to Shinoa, they make no comment to address this impression.

Even when Shinoa asks if Mahiru is in Guren's sword since she heard him call her name, Mahiru-no-Yo does not react when Guren speaks that Mahiru is already gone since she turned into a demon and saved the world by completing Cursed Gear. After Shinoa asks him if Mahiru is together with him inside his sword, there is the concern that he is being possessed by her. When Guren asks her if they ever got along, Shinoa explains that she was not close with her sister because Hīragis are raised without knowing familial love.

In Shinoa asking if making use of Yu was one of Mahiru's orders, Guren is also questioned whether her half-sister or the demon for lack of a better word inside his sword is ordering him, she then asks him to stop what he is doing if his goal does not benefit Yu. Once more on these areas, Mahiru-no-Yo does not communicate anything regarding any previous or currently held intent. After Guren tells Shinoa that Mahiru is dead and is not coming back, he says that the demon inside his sword is under control. Asserting he is not being possessed by her, Shinoa does not believe him. It would transpire that Mahiru-no-Yo would be possessing Guren at certain points, and it would be possible for Mahiru to return once Mahiru-no-Yo was split back into her and Noya. For the moment, there is the possibility that a namanari succeeded in misdirecting Shinoa so as not to reveal any details, by giving the reassuring focus that Guren was not being possessed, where he may very well have been, to assure Shinoa this was not the case.

Nagoya Arc
After Lieutenant General Kureto Hīragi has detailed the campaign to target vampire nobles in Nagoya, Mahiru-no-Yo had evidently absorbed the conversation they had. Appearing after the talk had concluded, Mahiru-no-Yo whispers to Guren in order to remind him to follow her rather than Kureto.

"No, Guren. You won't. You'll follow me, right?"

- Appearing to Guren when Kureto tries to lure him to his side.

At the Ebina rest stop, Guren punishes Shinoa squad, and in the sparring match Mahiru-no-Yo is used against Yu's Asuramaru blade. A powerful red whirlwind is released from the Mahiru-no-Yo sword to destroy the doors where Shinoa and Mitsuba are also hurled away. After the fight, Shinoa charges at Guren only for her scythe to get knocked away using Mahiru-no-Yo.

Used in the operation to wipe out a large number of vampire nobles in Nagoya, the Mahiru-no-Yo weapon helps defeat Mel Stefano. Afterwards, Guren moves to his next targets on his list Thirteenth Progenitor Crowley Eusford, along with seventeenth progenitors Chess Belle and Horn Skuld. When Crowley was overpowering him, Mahiru-no-Yo's energies were poured into the ceiling by calling out its name to release dark crimson sparks.

Passive when Guren eventually gets captured by the vampires after the fight with Crowley, he was seen near Krul Tepes and a few of her soldiers. Where Guren was being beaten by an angered noble, Guren's hair was grabbed for him to be raised up to his face. After Guren spits on the noble's face, the vampire curses him and kicks him to the ground with threats to kill him. At this point, Mahiru-no-Yo appears to cradle Guren's head on her lap. Consequently, Guren's personality begins to change as Mahiru-no-Yo possesses him and turns him into a namanari.

In this state, the sword appears to have a will of its own as it unsheathes itself. Invisible to others, Mahiru-no-Yo within Guren easily beheads the noble, and she holds the weapon for Guren to take. Guren's personality would visibly become demonic and heartless, however even in this state they could not defeat third progenitor Krul Tepes. For all the increased strength, they would be swatted away by the third progenitor. Having arrived at the airport in Nagoya where a sacrificial experiment is being held by Kureto and Aoi Sangū on the survivors of the Moon Demon Company, Guren raises up his sword to take part. The weapon is brought down upon Yu, before being blocked by Mika, before they clash further.

Chains wrap around Guren's arm as the curse consumes him. Speaking the words to drink the blood of human sacrifices, demons, and the progenitor, this proclamation turns the Mahiru-no-Yo sword from black to a complete pure red color similar to first-class vampire weapons. The blade is then used by Guren to slaughter both vampires and humans, where Mahiru-no-Yo helps provide blood to power a seraph.

When Mirai Kimizuki as a seraph has brought calamity to the world, the Mahiru-no-Yo sword runs through Kimizuki when he attempts to reach his sister. It is also used to stab Yu when he tries to speak with Guren. Although complicit in this act, Mahiru-no-Yo does urge Guren to not wake up so he would not be affected by this. After Yu stops the demon Abaddon using the power of the Second Trumpet, Mahiru-no-Yo remains in possession of Guren as he advises Yu to do it and break their taboos. Where Guren indicates he will pursue Yu, he is stopped by Shinya who is livid about the betrayal of so many of his men. While Mahiru-no-Yo does not comments, Shinya realizes that Guren has been possessed.

Post-Nagoya Arc
After three months, Mahiru-no-Yo is held by Guren, who with Kureto can be seen walking through the vampire city of Sanguinem. Fighting together side by side, they battle against the vampires with their demon weapons, where they are commanded to attack the enemies before them. On his way back to Shinjuku, Guren injects a drug into his forearm while a soldier drives him. The drug suppresses his demon.

Osaka Arc
While Guren is driving away with his squad, he reminisces back to eight years ago, when he triggered the Apocalypse by reviving his friends where they could survive for the next ten years in order to be with them. Electing to manifest, Mahiru-no-Yo warns Guren that if his team ever learned that they are actually dead, they will turn to dust. Upon being told to disappear, Mahiru-no-Yo goes to the roof to find Shinya's demon, Byakkomaru there. With Byakkomaru demanding that Mahiru-no-Yo identify herself as they are not a demon; in response, they wonder what he would do about it. When Byakkomaru replies that he would do nothing, unless Mahiru-no-Yo harmed Shinya, they threaten to kill Shinya if he knows about her, then harshly silences Byakkomaru. Ordered to leave by Guren, they travel ahead of everyone to Osaka Bay. Mahiru-no-Yo can smell the scents of Shinoa and burning vampires, which leads her to go investigate the latter scent. Appearing right in front of an unsuspecting Ky Luc, they then look to the burning crosses holding Ferid and Krul who have been sentenced to sunlight exposure torture. In taunting a suffering Ferid, their presence is noticed.

Despite Ky Luc being unable to see Mahiru-no-Yo, an unsettling feeling is felt by him. Feeling he is right it is a ghost, Mahiru-no-Yo is not seen as Ky Luc tries slicing in its general direction. Having returned to where she came, Mahiru-no-Yo then appears on the road that Guren and his friends are travelling down. Waving to him, Mahiru-no-Yo signals the danger of the path ahead. After arriving at Ferid's mansion, Mahiru-no-Yo is summoned to knock out out the whole squad except for Shinya. Forming next to Guren, they comment that Byakkomaru is searching to kill to him. Hearing Guren say it is because they provoked him; Mahiru-no-Yo assists with the beginning fight.

Seeing Guren and Shinya getting ready to battle, Mahiru-no-Yo says that this is the first time the two are fighting over her since high school. When Guren denies this, Mahiru-no-Yo decides to announce that she will sleep with whoever wins, then claims it is his favorite scenario. Reappearing after Guren's victory, Mahiru-no-Yo watches over an unconscious Shinya. Wondering why Guren brought his squad here, Mahiru-no-Yo reminds him that they could be destroyed if they find out the truth. Though not receiving an answer, Mahiru-no-Yo realizes that Guren is close to becoming a demon, thus he purposefully made his friends aware that he was hiding something to maintain his grip on his humanity. When Guren tells them to leave him alone, Mahiru-no-Yo mentions that he has the power to banish her whenever he wants to.

"What a peaceful sleeping face. Guren? Why did you bring Shinya and the others here? You had multiple other options. In fact, there was no need to act like you had secrets to hide in the first place. If they discover what happened, they'll vanish. That isn't a risk worth taking. So why did you do this? ...You've hit your limit, haven't you? Your heart can't take much more of this. If you didn't let your friends know that you were keeping secrets, that you were weak... then you'd become a full demon. That's why you told them. The drugs aren't enough anymore, are they? You must do things that go against your ideals... or you'll become a true demon—"

- Posing questions, then offering her own answers on why Guren brought his friends to Ferid's mansion.

She later manifests in front of Shinoa, and expresses joy over seeing her alive and well. Mahiru-no-Yo then wonders why Shinoa is unable to see her. Feeling that Shinoa should exceed her as an experiment, Mahiru-no-Yo registers that her demon has not awakened. They detail that love, more specifically sexual desire and lust, will corrupt Shinoa until she no longer cares about the world. Mahiru-no-Yo stared at the gathering squad and noticed that Shinoa has her eyes set on Yu. From him, Mahiru-no-Yo glances down to Shinoa, and sees that her younger half-sister is gazing at Yu. With that, Mahiru-no-Yo leaves telling Shinoa how much she is enjoying this.

After, she appears beside Shinoa when Guren is explaining the being that has been controlling the Hīragis. Silent, Mahiru-no-Yo frowns upon seeing Shinoa feel a pain in her chest. Where Mahiru-no-Yo came across them both before, Guren and Shinoa squad are to free Krul and Ferid from their sunlight exposure torture due to needing information. During the battle against their guard, Mahiru-no-Yo is summoned by Guren to engage Ky Luc. With them there, it delivers the uneasy feeling that Ky Luc experienced before.

Shibuya Arc
When the talk between Kureto and Guren comes to an end, the former decides to attack him and Shinya. Summoned, Mahiru-no-Yo allows Guren to defend himself. Noticing that Kureto has a great surge of power when he drew Raimeiki, when Shinoa comments this is bad, Mahiru-no-Yo agrees. Perceiving Shikama Dōji floating behind Kureto, they alert Guren that Kureto is being possessed by some unbelievably powerful monster.

Later on, Guren notices Mahiru-no-Yo manifest close by after hearing Shinoa talk about how Shikama Dōji may have possessed her. They listen to Shinoa talking about how Mahiru gave up her life for to protect her from Shikama Doji, with any hope of a relationship with Guren gone. Shinoa teases Guren that it is because of her that Mahiru-no-Yo never got to be together with Guren despite their love. After hearing Guren speak that the past does not matter now that the catastrophe destroyed the world, and how the past is gone and will not be back, where it is added that they should focus on the present situation and what they can do now, Mahiru-no-Yo complements Guren on his speech. Manifested, Mahiru-no-Yo sits next to her sister, yet cannot be seen by Shinoa.

When Guren and Kureto discuss how Shikama Dōji went after Shinoa instead of Kureto since she is Mahiru's sister, Mahiru-no-Yo manifests and they listen to their conversation silently. Hovering nearby to Shinya, they glance to frown at him since Guren knows he cannot let the dead realize they have been brought back to life or they will return to dust. Where Kureto suspects the monster went after Mahiru first, Mahiru-no-Yo makes no comment on that, or on speculation on why she approached Saitō. However when Kureto asks Guren by who or what is he possessed by and who is imprisoning him, Mahiru-no-Yo answers aloud that the question is easy. While embracing Shinya around the neck from behind, undetected by others, Mahiru-no-Yo speaks that Guren is prisoner to love and friendship before asking him whether that is not right. After the escape of Shinoa due to Saito's arrival, Mahiru-no-Yo manifests and tells Guren it will not be long before Saito and Krul arrive. Further, Mahiru-no-Yo adds it is time to betray everyone just as both of them planned, which gains agreement from Guren.

Mahiru-no-Yo continues urging Guren on betraying everyone even more, with assurances that it will only take a moment. They encourage him to let himself change to become the other Guren.

Contently asking him once more if he is ready to turn into a demon, Mahiru-no-Yo informs him they would give lots of encouragement when Guren alludes to declining. Declaring that he is silly, Mahiru-no-Yo asks what he is going on about, failing is easier than succeeding since he could escape his responsibilities. Hugging him, they call Guren a crybaby then asks if he is scared. With the answer being in the affirmative, they question since when. A flashback occurs when as Mahiru, she first met Guren and was taken away from him.

Appearing concerned as they listen to Guren speak about how she had no one there to help her, and so no choice but to become a demon, Mahiru-no-Yo states that is not his fault. The catastrophe was going to happen, it was planned that way and if Guren had not done it, someone else would have. Trying to alleviate his guilt, Mahiru-no-Yo holds Guren tightly and tells him it is both their fault, and now he is trying to take responsibility for it. They assure him it is okay, and not to worry, he will do it right and succeed. Seeing the chains emerge from Guren, they supports this by telling him he is doing well and to keep it up. Mahiru-no-Yo assures Guren they will keep him safe. Intending to take half the demon into them, Mahiru-no-Yo will not allow Guren to go berserk.

Noticing that Shinya and Guren's squad have found them, Mahiru-no-Yo resumes persuading Guren to close his eyes and dive inside for Shinya, to save all of them. After some chains are shot, Mahiru-no-Yo makes eye contact with Shinya who can see them, and is also perplexed at this fact. Mahiru-no-Yo reasons that it is because Guren is holding half the demon now. With Shinya's rifle aimed at them, they are demanded to say what is being done to Guren, but the reply is that is a secret. Holding Guren, Mahiru-no-Yo laughs off Shinya's declaration to kill them, telling him he does not have the power to do that. In response to Byakkomaru being called upon, Mahiru-no-Yo verbally activates the chains. With other squad members now able to perceive them, Mahiru-no-Yo has had enough of this nonsense and orders Guren to close his eyes. Once inside his mind Guren sees his sword thrown through Mahiru-no-Yo's chest who lays on the ground unconscious. Suddenly they scream in pain and Noya erupts out of the body. Although Mahiru-no-Yo was separated into Mahiru Hīragi, and Noya, the two beings that make them up, Mahiru-no-Yo often as a weapon based power can still be invoked as the singular being even though Mahiru is apart from Noya. The power emanating from the two bodies, combined with Guren as a demon, and powered collectively further by chains were referred to as Mahiru-No-Yoru and were capable of combining their powers.

The blade's name Mahiru-no-Yo is spoken by Guren when used to stab through Mirai. Used to murder her, the act also causes a sinful key to be emitted from Mirai. The sword is then used in the fight against Shikama Doji who is possessing Shinoa's body.

With Mahiru, then Noya returned to Guren's sword they could still be invoked individually but the cursed gear gave Guren greater power when they were within him. Whilst they could not see, they could sense the sheer mass of invisible swords that had surrounded Guren. Mahiru-no-Yo the sword was called upon to return and crush Yu's heart which it done by flying into his back.

Powers and Abilities

 * Demon's thrall: Mahiru-no-Yo may enter their host's mind and consume them with illusions in an attempt to break their will. If Mahiru-no-Yo wins, they gain control over the physical body. This was achieved on occasion, with Mahiru-no-Yo able to articulate her own views to others physically where they are unable to communicate otherwise. After merging with Noya, it should be noted that all Noya's previous abilities are now in Mahiru-no-Yo, making her a very powerful demon.


 * Basic form: The weapon Mahiru-no-Yo appears as a black katana with a red streak down the middle. 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 sword itself went from being almost black in color to purely red of all the blade length similar enough to first-class vampire weapons used by the progenitors when they drank their blood. Something similar took place 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 turn his demon into completely from black to fully red without using or placing a type of talisman on it.
 * Generating debilitating pressure: 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 range, victims pass out unconscious on the floor if they do not have the strength or willpower enough to overcome it. However, if the targets have high psychic based resistance, used wards, or are a potential candidate for the Black Demon Series, they range from enduring the energy, to outright being indifferent 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 that induces such effects.
 * Augmenting a host's capabilities: Merely drawing the sword increases their bearer's physical abilities significantly. When powers are invoked, it is often a shadowy based energy that emerges from the sword. Calling upon their name results in a greater amount of power being deployed to increase capabilities tremendously. Having Mahiru-no-Yo possess a host, their apparition can appear and enshroud the blade. The arm wielding it has streaks of overwhelming flames, powerful enough to create an explosive force in the midst of the vicinity. Slashes can send these flames hurtling towards foes.
 * Anime: whirlwind: 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 energy. More so, the demonic aura can be seen concentrating all around its inner layer and then being destructively launched at targets upfront within his range. This red whirlwind was able to demolish the concrete wall of a building, and propel half of Shinoa squad away.


 * Defensive measures: Able to be used to devour an enemy's attack, if Guren was acting defensive, he would then call on the demon blade's name to assist him in battle. On one occasion, when Guren was knocked far back and sent flying to the ceiling, he could then used the demon's power and ability to cushion the physical impact.
 * Namanari: A Namanari is a human one step from becoming an actual demon. Mahiru-no-Yo has managed to turn Guren into one of these. In this form, Mahiru-no-Yo and Guren co-operate for a common, usually murderous goal, where they have tremendous power. However, with Mahiru-no-Yo's influence, Guren's personality changes to a more demonic, and heartless. It is more insistent on what it wants, and acts to acquire it. It is unclear whether this is the demonic side of Guren that Mahiru began to create the summer before the Apocalypse when they were both human, or if it is Mahiru-no-Yo's true nature coming through as the one in control of Guren's body.

Once Guren is possessed by Mahiru-no-Yo, the blade would behave as if it had a mind of its own. Unsheathing itself from the scabbard, the sword then proceeded to move around on air swiftly. Its newfound aptness allowed the weapon to behead a vampire noble. In the manga, it was after that occurred when Mahiru-no-Yo appeared as a ghostly apparition with mass-like demonic aura. Mahiru-no-Yo levitated over Guren while his katana is equipped under them.

Equipment

 * Talismans: Even after becoming the demon Mahiru-no-Yo, they still use talismans, particularly unique ones, and skilfully. Mahiru-no-Yo also has exploding spell-tags, using them with the same skill as Mahiru did.

Seraph of the End: Vampire Reign
Quotes from Seraph of the End: Vampire Reign: "Demand it! Ask for it! Seek out more power!!"

- Mahiru-no-Yo to Guren.

"Aah... I can smell Shinoa's scent. She must be close. That... and I smell burning vampire... Aha ha! Someone is getting roasted like a side of beef."

- Able to sense her younger sister's presence, then a gruesome comment about Krul and Ferid as they being burnt.

"Aah, this brings back memories of high school. Once again, my lover and my fiance are fighting each other over my hand..."

- While not as outgoing, there are features of Mahiru's mannerisms when viewing Guren and Shinya.

Trivia

 * Her demon name Mahiru-no-Yo 「真昼ノ夜」 means "Midday's Night."
 * In the manga, Mahiru-no-Yo is the only one who could sense that Shinoa's demon has not awakened yet. Their view that she requires love and lust to allow for Shikama Doji to awaken eventually happened.
 * According to the official Manga 8.5 Fanbook:
 * Interests/Likes: Guren's future, ambition, lust, the "Seraph of the End" experiment
 * Favorite food: Human hearts/minds, demons, cake
 * Crush: Guren
 * Though Mahiru-no-Yo is a demon, they retain all of Mahiru's memories in her previous life prior her death. For Noya's part, it is not memories, but the impulses of a possession demon that come through.
 * When they became separated back into Mahiru and Noya, Guren turned into a namanari with him in control.