In the 14th year of the Genroku period, Asano, the head carpenter of Edo Castle, attacked Kira, the master of ceremonies, with a sword, leading to Asano's forced suicide and Kira's punishment being overlooked. Over a year later in Edo city, Shimohashi Hyogo, a carefree ronin and the nephew of Yagyu Yoshitaka, is ordered by his uncle to investigate the activities of the Ako Ronin, a group sympathetic to Asano's cause. However, Hyogo, who sympathizes with the Ronin's plight, helps out in times of need, rescuing Oishi Kuranosuke and Horibe Yahei from danger. He also teams up with Yaenosuke, a newspaper publisher, and Otaki, a geisha, to plan an attack on Kira's estate.
