Hajime Shiroishi, called Ichi, is a tormented soul forged in the crucible of a traumatic upbringing. During his youth, he suffered relentless bullying from peers and withering emotional neglect from parents fixated on his academic failures. A biology class experiment—dissecting a live frog—sparks a disturbing awakening to violence’s erotic charge, later amplified by a roadside encounter with roadkill that drives him to methodical experimentation on rabbits. These acts cement his sadistic compulsions.

Repressed traumas fester within him—memories of betrayal by a blackmailing friend and years of humiliation—fueling volatile mood swings. His psyche fractures into emotional extremes: tearful vulnerability and juvenile mannerisms clash with lethal martial arts precision, honed alongside a concealed boot blade. Manipulated by a cunning elder dubbed the Old Geezer, Ichi becomes a weaponized pawn, his instability exploited to mold him into a living killing tool.

His crimes follow a ritualized brutality merging pain with perverse arousal, each gruesome act intertwined with sexual gratification. Graphic sequences of carnage unfold against pulsing techno soundscapes, mirroring the frenzy of his violence. Yet fleeting self-awareness pierces his madness—retching episodes or paralyzing guilt hint at fractured morals battling his impulses.

Ichi’s arc traces the cycle of abuse, shifting him from bullied victim to unhinged predator. Enmeshed in yakuza schemes, his chaotic actions disrupt criminal hierarchies even as he remains trapped in others’ machinations. The narrative threads his unraveling to systemic bullying, familial abandonment, and warped mentorship, framing him as a warped mirror—simultaneously embodying and indicting society’s capacity for violence.