Shiro Ishi is a quiet and seemingly cowardly high school student who harbors a deep, unnerving fascination with violence. He spends his time watching the school's strongest fighter, a boxer named Dai, brutalize others. While everyone else sees a bully, Shiro watches with a wide, unsettling smile, not out of mockery but because he derives a perverse enjoyment from the spectacle of the fights. This behavior is misunderstood by Dai, who becomes fixated on Shiro, believing the smaller boy is laughing at him and thus challenging his authority. The school environment is a brutal hierarchy where bullying is rampant, and even younger children in Shiro’s karate class taunt and physically abuse him for his apparent weakness, yet he consistently refuses to unleash the anger building inside him. The setting is a gritty, early 2000s Japanese high school where social order is maintained not by teachers, but by physical dominance.

The tense status quo is shattered by the arrival of a violent transfer student named Onizame. Unlike the brawling Dai, Onizame is a merciless fighter who uses an arm-breaking hapkido style, swiftly crippling anyone who gets in his way to establish himself as the new king of the school. In his first major confrontation, Onizame easily defeats and severely injures Dai, leaving him broken on the ground. Rather than seeking out Dai again, Onizame turns his attention to Shiro, having heard a rumor or sensed that the unassuming student might actually be the only one capable of providing him with a real challenge. This forces Shiro into a collision course with two violent predators: Dai, who is obsessed with him, and Onizame, who wants to test him.

As the pressure mounts, Shiro finds himself kidnapped by thugs from a rival school who mistake him for an ally of Dai. Left alone with his tormentors, Shiro finally snaps. Triggered by the extreme stress, he taps into a hidden, murderous rage that lies just below his cowardly surface. The results are catastrophic; although the specifics are left ambiguous, the thugs are left utterly destroyed. Onizame witnesses the aftermath and is the only one who understands that Shiro possesses a terrifying, uncontrollable strength. When Dai intervenes in a final confrontation to save Shiro, he is again overpowered by Onizame and nearly killed. Watching the violence escalate, Shiro becomes sexually aroused, and as Dai is about to be murdered, Shiro unleashes his full, primal power. In a frenzy of terror and ecstasy, he brutally destroys Onizame, saving Dai while screaming and laughing, culminating in a violent orgasm. This event marks the psychological birth of Ichi, the killer, setting the stage for his future as a legendary figure of chaos.