Byakkomaru

Byakkomaru (白虎丸) is a high-ranked manifestation-type demon of the Black Demon Series. He formed a contract with Shinya Hīragi and became his Cursed Gear.

Appearance
Byakkomaru's weapon takes on the form of a black, green striped sniping rifle with a bayonet attached at the end. It can either fire off a rapid succession of projectiles or fire a single bullet to manifest Byakkomaru.

Byakkomaru manifests as a gigantic white tiger, surrounded by bright blue flames. The tiger can split into multiple tigers in manifestation form to strike down its targets.
 * In the anime, the bayonet has been shown pointed downward to help support the rifle while Shinya is sniping.

In Chapter 83, Byakkomaru is shown to have a human form. His human form wears a white tiger pelt headdress that covers the top half of his face. Like all former vampires, he has red eyes (which aren't always visible) and fangs but it's unknown if he has pointed ears (though it's very likely he does). Along with that, he wears a longish Japanese style vest over a black shirt with long, small, flowing sleeves and black pants. Finally, he wears longish black gloves with a white section on the palms and black boots.

Personality
Unlike most other demons, Byakkomaru seems to be very protective over Shinya, as he warned Mahiru to keep away from him, and grew agitated when the latter threatened to kill Shinya if he finds out what she's plotting.

However, he does not seem to care about other matters, shown when he told Mahiru that he doesn't really care who she is and what she is, as long as she does not harm Shinya.

Byakkomaru seems to be more a wise demon and calm, having never asked Shinya for desires repeatedly who unlike most demons does, as he cares for Shinya's well being.

History
Byakkomaru's past is mostly unknown, but judging by Byakkomaru's red eyes and fangs , he was once a vampire before somehow becoming a demon. At some point, he got sealed inside a Cursed Gear, and later in the year 2012, became Shinya Hīragi's gear.

Events of 2012
Byakkomaru was contracted with Shinya. According to the light novel, Shinya underwent an operation to increase his chances of handling a Black Demon Series Weapon, and he emerged from the operation successfully. Ever since then, Byakkomaru became his primary weapon.

Events of 2020
Shinya uses Byakkomaru in battle against the vampires.

Osaka Arc
In Chapter 54, he manifests to confront Mahiru Hīragi on the roof of a moving car. He demands to know what Mahiru is as he says that she is not a demon, and threatens her if she tries to harm Shinya. He reappears again in Chapter 56 to warn Shinya that Guren is trying to kill him; and when Shinya is getting ready to fight Guren, Byakkomaru is confident in Shinya's chances of winning due to the advantage of distance, but is told to not always expect things to go as planned.

Shibuya Arc
The white tiger energy is fired at a Hyakuya agent during the attack on Shinjuku only to be deflected by the weapon form of Jigenso. Multiple forms are launched only to travel into Crowley when the agent opens a portal to achieve that end.

Later, Shinya asks Byakkomaru to give him more power, however Byakkomaru refuses to do so advising Shinya that Guren isn't wielding a normal demon. Shinya doesn't care but Byakkomaru says otherwise, explaining to him that he is always being aloof, and isolated from everything but he still hold burning desires. He says how he stole the lives of others just to survive and he feels nothing what so ever that includes even in likelihood when faced by death. Byakkomaru continues to lecture Shinya about his previous actions including when he used to be Mahiru's former fiancé, or when he killed many children just to survive, he still feels empty. A young Shinya says there is no need so, Byakkomaru says that to make an effort to acquire a thing but then loses it, Shinya then says being that's the case, efforts are meaningless to which Byakkomaru agree's.

Byakkomaru informs him that Guren is beyond saving now being the case telling him to run, but Shinya insists on saving Guren much to Byakkomaru confusion telling him as to why he is so obsessed with him. The young Shinya simply states he should know being his demon. Byakkomaru answers that he has what does he not, such as he is different living in a world much worse, filled with despair and helplessness to which he was born in a family just for the Hiiragi's to ridicule him, burdened with a fate that he will never get. Shinya in happiness says that he never gives up no matter how many times he fail as if he is looking at him as an idiot, Byakkomaru says that Shinya hate idiots which he agree's even saying he might abandon Guren. Byakkomaru agreeing with him to abandon him that of which Shinya would perhaps do. Shinya laughs saying in a joking matter that he will but Byakkomaru is confident he wouldn't as it's contradictory. Byakkomaru says as if he is in love with Guren.

Shinya doesn't completely agree mentioning it's just a simple idolization, understanding why Mahiru chose Guren instead of him, Shinya again says that Guren just purposely let himself getting hurt over and over again although he never gives up wanting Byakkomaru's help now but Byakkomaru insist's that saving him and he will die without enough power, Shinya agree's. Byakkomaru informs him that he is wise and dying here will be stupid of him and he questions him again if he is serious that he intend to die, Shinya simply answers by saying how good question it is. Byakkomaru caring for him and doesn't want any harm for Shinya, being his demon after all. Shinya implies that he doesn't care either way, living or dying nothing makes a difference but he would've had a regret if he were told to die right now. Finally Shinya mentions that Guren hasn't given up on living up or anything and he would get annoyed to no end just for him to give up before him and tells Byakkomaru to devour his desires and Shinya doesn't care if he turns into a demon. Byakkomaru finally gives up on him after he names his desire which that he will never give up on Guren and gives him the power he wants.

Forms and Abilities

 * Demon's Thrall: Byakkomaru can enter it host's dreams and memories to create nightmares and break it's host's will. This is done in order to take over his body. This ability can only be used against his host.
 * Basic Form: Byakkomaru takes the form of a black, green striped sniping rifle with a bayonet attached at the end . Byakkomaru's specialty is long-range firing, and it is not very effective in close-range combat.
 * Multiple White Tigers: Shinya can fire bullets which splits and then manifests into several tigers. Each tiger can strike its target independently.
 * Hidden Bullet: Shinya can fire a bullet which appears behind his target, as shown when fighting with Yūichirō Hyakuya in chapter 17, "Cursed Guinea Pig." It is shown to be an effective surprise attack, but Shinya revealed to Yu that he can only activate that ability once for an unspecified amount of time.

Shinya Hīragi
Byakkomaru is Shinya's cursed gear. He is protective of Shinya as seen when he threatens Mahiru he will do something if she hurts him. And also when Guren knocked everyone out except for Shinya; he tells Shinya that Guren is not to be trusted any longer because it could put Shinya in danger. Byakkomaru works close enough with Shinya to target specific enemies.

Mahiru Hīragi
Byakkomaru meets her for the first time when Guren Squad goes to Osaka. He is cautious of Mahiru because he can tell she is not a demon but chooses to do nothing about it.

Guren Ichinose
Byakkomaru warns Shinya that Guren is trying to kill him; and when Shinya is getting ready to fight Guren, Byakkomaru is confident in Shinya's chances of winning due to the advantage of distance, but is told to not always expect things to go as planned.

Quotes

 * "What are you? You are no demon."--To Mahiru Hiragi, Chapter 54, "Sinner's Christmas"
 * "But if you even think of harming Shinya--"--To Mahiru Hiragi, Chapter 54, "Sinner's Christmas"
 * "Shinya. You must not trust him anymore. He will kill you."--To Shinya Hiragi, Chapter 56, "Loose-Lipped Vampire"

Trivia

 * In the fanbook, it is revealed that the tigers are fired from the rifle. Shinya fires a single bullet, which then manifests into Byakkomaru's tiger form.