Mahiru Hīragi

Mahiru Hīragi 「柊 真昼, Hīragi Mahiru」 is the love interest and demon weapon of Guren Ichinose. She was also the next successor to the main house until she turned into a Cursed Gear called Mahiru-no-Yo. She also stole Krul's brother Asura from her and used him as her own Cursed Gear.

Appearance
Mahiru has long ashen hair with a front fringe and brown eyes; after becoming a demon, she has red eyes. Unlike her younger sister, Shinoa Hīragi, she has a taller, well-developed figure.

She is usually seen with her school uniform, a sailor fuku.

Personality
According to Shinoa, she has no qualms about betraying family. The fact that she became a possession-type demon suggests she is particularly violent.

In the light novel, Mahiru is shown to be extremely merciless towards those she considers an obstacle in her path. She is seen knocking out Guren's squad and attempting to choke Shinya during their first mission to investigate - and then exterminate, a Horsemen. She forced Guren to get possessed by a demon so he could join her and rule the world.

However, she is seen to truly care for Guren, crying when Guren cuts off his own arm to stop the demon from taking over and frantically trying to reattach that broken arm. She explains that she had given up on everything; betraying her family and the Hyakuya Church just so she could be with Guren. In the prologue of Volume 3, she said to Shinya that sometimes she wish that she's just an ordinary girl, and not the heiress of the Hīragi family.

History
Mahiru along with her younger sister Shinoa, were conceived through artificial insemination using the seed of Tenri Hīragi in a demon-possessed woman.

Mahiru was in love with Guren since they were children; but Guren was not welcomed by her family, so they were forcefully separated at a very young age.

When he was ten years old, Shinya had been selected by the Hīragi family to be the potential mate for Mahiru, and he was adopted into their family to this end. This was a plan by the Hīragi to keep their bloodline strong. However, when Shinya and Mahiru first met she told him she wouldn't fall in love with him as she already had someone. Had she openly stated to her family she didn't want Shinya, they would have disposed of him; and she wasn't allowed to be with Guren, whom she loved. For these reasons, they both agreed Shinya would be her cover-up fiancé until she could be with the person she loved.

Growing up, she saw visions of the future and even prophesied the end of the world on Christmas Day 2012 as God's punishment against human ambition for meddling with the taboo. The trumpets of the Apocalypse would sound, and the Seraph would descend.

Later on, her research on demons eventually turned her into one until Guren killed her. She became the demon within his Cursed Gear and part of the Black Demon Series.

Story: Manga
Although she is present as Lieutenant Colonel Guren Ichinose's weapon from the moment Guren appears in the manga, readers first see her human appearance at the beginning of chapter 17 within his mind. She wants him to seek more power. When he addresses her, she says she's glad that he came as she wanted to meet with him.

Post-Shinjuku Arc
In the following chapter, Guren reveals her 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 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 years ago, 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 Hīragis are raised without knowing familial love.

Shinoa 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 inside his sword is ordering him. She then asks him to stop what he is doing if his goal does not benefit Yu.

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.

Nagoya Arc
In chapter 23, she appears and whispers to Guren in order to make sure he follows her rather than Lieutenant General Kureto Hīragi.

She appears again in chapter 38. She possesses Guren and kills the noble beating him. She uses Guren's body to point a sword at Krul Tepes and states that Krul will help her conduct an experiment on the Seraph of the End at Nagoya Airport.

Forms and Abilities

 * Demon's Thrall: Mahiru-no-Yo may enter her host's mind and consume him with illusions in an attempt to break his will. If she wins, she gains control over his body.
 * Basic Form: Mahiru-no-Yo appears as a black katana. Merely drawing her increases her bearer's physical abilities significantly and calling upon her name increases them tremendously.

Trivia

 * Mahiru 「真昼」 means "Midday"
 * Hīragi 「柊」 means "Holly."
 * Her demon name Mahiru-no-Yo 「真昼ノ夜」 means "Midday's Night."
 * According to the official fanbook:
 * Interests/Likes: Guren's future, ambition, lust
 * Favorite food: Human hearts/minds, demons
 * Crush: Guren

Manga

 * "Demand it! Ask for it! Seek out more power!!"--The demon Mahiru Hīragi to Guren, Chapter 17, "Cursed Guinea Pig"
 * "Oh, Guren! You came. I was just thinking I'd like to see you."--The demon Mahiru to Guren, Chapter 17, "Cursed Guinea Pig"
 * "No, Guren. You won't. You'll follow me, right?"--The demon Mahiru to Guren when Kureto tries to lure Guren to his side, Chapter 23, "Ambition in the Demon Army"