In the year 1844 of the Edo Period, as the Tokugawa Shogunate is in decline, the sadistic Lord Matsudaira Naritsugu of Akashi Domain rapes, tortures, and murders his citizens at will. He is shielded because the Shōgun is his half-brother. Sir Doi Toshitsura, the Shōgun's Justice, realizes that the slaughter will escalate when Naritsugu ascends to a higher political position. After the head of the Mamiya clan publicly commits ''seppuku'' as a way of showing disdain for Lord Naritsugu, who personally executes his entire family, SirDoi seeks out a trusted older samurai, Shimada Shinzaemon, who served under the former shōgun, and secretly hires him to assassinate Naritsugu. However, Naritsugu's loyal retainers, led by Hanbei, an old contemporary of Shinzaemon, learn of the plot by spying on Doi.