Kumokiri Nizaemon, a former samurai warrior, has abandoned his class to become the leader of a gang of thieves. He leads his outlaws in an attempt to rob the castle of his former clan.
Japan, 1860. The men of the Mito clan, victims of the Ansei purge, anxiously prowl around the Sakurada Gate of Edo Castle with the intention of assassinating Naosuke Ii of Hikone, tairō of the Tokugawa shogunate and responsible for their misfortune.
The story tells of a group of samurai who were left leaderless (becoming ronin) after their daimyo (feudal lord) was forced to commit seppuku (ritual suicide) for assaulting a court official named Kira Yoshinaka, whose title was Kōzuke no suke. The ronin avenged their master's honor after patiently waiting and planning for over a year to kill Kira. In turn, the ronin were themselves forced to commit seppuku for committing the crime of murder.
The plot is based on the novel "Akechi Samanosuke no Koi," the final work in a trilogy by Hiroshi Kato about the forced suicide of Oda Nobunaga at the temple Honnoji. Historically, the general Akechi Mitsuhide is credited with causing Nobunaga's downfall. Kato's novel focuses on Mitsuhide's nephew Samanosuke, who fought alongside his uncle during the assault on Honnoji.