Ichibanboshi hates samurai since his family was killed by them. However, when attacking samurai with the same strange mask he saw that day, he is arrested. Along with others, he receives an unexpected and surprising offer: Toudou Heisuke, the eighth commander of the Shinsengumi, a famous historical group that serves as a police force in Kyoto, offers to enter the group in lieu of an execution. Ichibanboshi will have to become what he hates most to complete his revenge: a samurai.