In the Genroku era, after Lord Asano's forced suicide, Chief Retainer Juzaemon sends Kaizuka Shingo undercover to uncover Oishi Kuranosuke's vengeful plans. Meanwhile, Kira's son, Tsunanori, uses spies to thwart them. Drawn to Oishi's honor, Kaizuka joins him, leading to a climactic raid that defines loyalty and justice.