In the distant past, fiendish beings called Oni slaughtered people and wreaked havoc for their own amusement. A solitary hero, Momotarou, dared to confront these brutal, almost invincible monsters, yet the conflict was only just beginning.
In a far‑future era, impulsive firearms aficionado Shiki Ichinose lives a relaxed life. That changes abruptly after he is expelled from school. Immediately, a man assaults him, but Shiki is rescued by his adoptive father, Tsuyoshi. While escaping together, Tsuyoshi confesses that Shiki is actually a bloodline descendant of the Oni, and that both he and their attacker belong to the Momotarou line.
The two Momotarou families soon collide in a violent showdown, and Tsuyoshi gives his life to shield Shiki. Grief-stricken, Shiki awakens the Oni blood within him, granting colossal power but driving him into a berserk state. Though the foe slips away, Naito Mudano—a teacher of Oni at Rasetsu Academy—takes notice. Under Mudano"s tutelage, Shiki must master the Oni blood if he hopes to honor his father and seek revenge.
