Osamu Kogure is a young man recently released from prison, struggling to survive in poverty while living in an abandoned house and taking on odd jobs. His life takes a dark turn when his violent former prison senior, Inui, shows up and starts bossing him around. Inui forces Osamu to disclose the whereabouts of his ex-girlfriend, Koyuki, whom he then kidnaps and subjects to brutal abuse. During a robbery planned by Inui that goes awry, Osamu loses his left arm. Koyuki helps him seek medical treatment from a doctor connected to the yakuza, who uses an experimental drug to regenerate Osamu's arm. However, the new limb transforms into a monstrous beast-like hand, causing Osamu to lose control. As Osamu and Koyuki attempt to build a fresh start together, they find it impossible to escape the shadows of their troubled past.