| Director | Takashi Miike |
|---|---|
| Budget | $1.4 million |
| Box office | $80,631 |
A man named Ichi spies from a balcony, masturbating as he watches a pimp assault a prostitute. When discovered, he flees. Soon after, the sadistic yakuza boss Anjo is murdered. A cleaning crew led by Jijii disposes of the body and frames Ichi for the killing. Kakihara, Anjo's sadomasochistic lieutenant, inspects the spotless crime scene and assumes Anjo absconded with clan funds. He interrogates Karen, Anjo's girlfriend, and pursues false leads, eventually torturing Suzuki, a rival clansman. When Suzuki proves innocent, Kakihara cuts off his own tongue as atonement.
Kakihara later captures Kano, a member of the cleaning crew, who reveals Ichi's role in Anjo's death and warns that Kakihara is now a target. Meanwhile, Ichi returns to the pimp's balcony, witnessing another assault on Sailor, a prostitute he frequents. He kills the pimp but then turns on Sailor, murdering her when she resists.
Exiled from the yakuza, Kakihara takes the Anjo clan with him. Suzuki offers Jijii a bounty for Kakihara's death, unaware that Jijii manipulates the conflict, using Ichi as his weapon. Ichi, ordinarily timid, becomes homicidal when enraged, a trait Jijii exploits by implanting false memories, including a fabricated high school rape.
Ichi rescues Takeshi, the son of Kakihara's henchman Kaneko, from bullies. Later, Jijii provokes Ichi into slaughtering Anjo clan members in an apartment. Kaneko, recognizing Ichi from earlier, saves him from an attacker, recalling his own past rescue by the yakuza.
Kakihara employs corrupt twin detectives, Jirō and Saburō, to track down Myu-Myu, a prostitute linked to Jijii's associate Ryu Long. After Long escapes the detectives, Kakihara captures and tortures him for information. Meanwhile, Jijii manipulates Karen into seducing Ichi by posing as the woman from his false memory. Confused by her claims, Ichi kills her. Jijii then lures Kakihara into a confrontation, killing Takayama, one of Kakihara's men, before Ichi arrives and slays Jirō and Saburō.
The final confrontation unfolds on a rooftop, where Ichi—believing Kaneko is his brother due to Jijii's psychological manipulation—slits his throat in front of Takeshi. The traumatized boy attacks Ichi, triggering a mental breakdown. Kakihara, overwhelmed by Ichi's screams, impales his own ears with skewers, hallucinating Ichi decapitating Takeshi and attacking him. In his delusion, Ichi kills Kakihara, though in reality, Kakihara dies from self-inflicted wounds.
Years later, Jijii's corpse is found hanging in a park. A young man resembling Takeshi departs with a group of children, leaving the fate of the cycle of violence unresolved.