After a brutal assault by an imperialist criminal syndicate called the Masked Demons, the Shinsengumi's Eighth Division—the Kyoto law-enforcement unit loyal to the shogunate—is almost completely wiped out, leaving only Heisuke Toudou alive but critically wounded. Pressed by the local feudal lord, Katamori Matsudaira, to reconstruct the Shinsengumi, Toudou chooses to grant eight convicts an opportunity for redemption: they must discard their former identities and serve as replacements for the eight Shinsengumi captains. All but one agree; the dissenting convict is promptly executed by the former assassin Sakuya. Nevertheless, Toudou struggles to mold the seven reformed criminals into devoted subordinates. Ichibanboshi, who is impulsive and driven by vengeance after his family was killed by the Masked Demons, jeopardizes Toudou's plan due to his lack of discipline. While Toudou vows to defend the shogunate from imperialists and foreign invaders, rival factions, including Kogorou Katsura's group, begin advancing their own agendas with a single objective: to seize control as the Edo period draws to a close.