The Edo period, where the world is peaceful. Behind the peaceful lives of people, there was a special forces unit that only a limited number of people knew about them. Its name is "The Evil Fish Squad". The evil fish squad consisting of Rinzo, Surume, Funaemon, and Himechi, are all on death row inmates. In exchange for death penalty exemption, it is a secret force that is tasked with doing dangerous, dark work that is close to death. This time, the mission given to the Evil Fish Corps is to undercover investigation into a mysterious group, Otaikokyo. Meanwhile, a young man appears in front of the evil fish squad. His name is Mizuno Hirama. Hirama continues on a journey to find a sister who is far from home. Will the Evil Fish Squad be able to save the Edo town from the conspiracy of Otaikokyo? A beautiful and exciting battle between man-eating demons and rogues begins now.

Quatro prisioneiros no corredor da morte são enviados como o "Esquadrão Harakiri," uma unidade especial descartável pelo xogum, com a condição de serem poupados da pena de morte. Conseguirá a equipe turbulenta cumprir sua missão de derrotar os "demônios devoradores de homens" e devolver a paz ao país?