Tokyo Gore Police
The film is set in a near future chaotic Japan. A mad scientist known as "Key Man" (Itsuji Itao) has created a virus that mutates humans into monstrous creatures called "Engineers" that sprout bizarre weapons from any injury. The Tokyo Police Force has been privatized to deal with this new threat of engineers, so a special squad of officers called "Engineer Hunters" are created to deal with them. However, unlike the average police force, the Engineer Hunters are a private quasi-military force that utilize violence, sadism, and streetside executions to maintain law and order.
Helping the police force is Ruka (Eihi Shiina), a troubled loner who is very skilled in dispatching the Engineers. Along with helping the police, she is looking for the killer of her father, an old-fashioned officer who was murdered in broad daylight by a mysterious assassin. Ruka soon receives a new case to hunt down Key Man, but once she encounters him, he infects her by inserting a key-shaped tumor into her scar-riddled left forearm before disappearing. Meanwhile, after an infected police officer massacres the main precinct, the Tokyo police chief (Yukihide Benny) orders a city-wide crackdown on Engineers — indiscriminately executing anyone suspected of being one.
While continuing her investigation, Ruka visits Key Man's home, where he reveals the truth about their past. His father was a police sniper who resigned after a sniping operation gone wrong. Desperate to keep his family out of poverty, he was paid to assassinate Ruka's father, who was leading a rally against the privatization of the police force. But shortly after gunning down Ruka's father before her eyes, he was murdered by the police chief — the real mastermind of the assassination — in front of Key Man. Swearing to avenge his father's death, he injected himself with the DNA of several infamous criminals, mutating him into his present form. After realizing that she and Key Man are seeking vengeance on the same man, Ruka slices him in half with her katana before heading back to the precinct. On her way, she witnesses the police force brutalizing civilians accused of being Engineers. When her bar owner friend (Ikuko Sawada) is drawn and quartered, Ruka's left arm mutates into an alien-like head with razor-sharp claws before she beheads the officers behind the execution. During her rampage, she is shot in the right eye, but her body quickly replaces it with a cybernetic eye. She confronts the police chief, who admits to her father's assassination, but explains that he raised her to become the perfect Engineer Hunter as atonement. Following a grueling sword fight, Ruka dismembers and eventually decapitates the police chief — effectively bringing down his reign on the police force.