This is what happens when an OVA decides ultraviolence is not a problem to solve but a language to speak. Every punch rewrites anatomy, every confrontation treats the human body as a thing that can be remade by sheer impact. The animation is rough enough that it almost looks like the brutality is happening in real time, unfiltered, and that's the entire point. A man walks into a prison designed to break him. What comes out is something that breaks back harder.

Saiga Riki-Oh is a young man with inhuman strength. After taking revenge on the yakuza boss responsible for his girlfriend's death, he lands in a maximum security prison run by a private organization. The prison is split into four blocks, each ruled by a member of the Gang of Four: a tattooed knife fighter who runs his block like a mafia family, a giant of enormous strength, an effeminate fighter cultivating opium, and a small man who fights with sewing needles. This single action OVA retells the prison arc of the Riki-Oh manga.