Shinnojo Mimura is a lower-ranked samurai who is employed by his clan as a poison taster. He has lived a thrifty but happy life with his beautiful wife Kayo and their old servant Tokuhei. However, his happiness comes to an end when he becomes blind after eating shellfish that is accidentally put into the lunch for the clan. Shinnojo cannot stand spending the rest of his life in darkness, so he tries to kill himself, but Kayo and Tokuhei manage to save his life, and he gradually becomes used to living without sight. Yet, one day Shinnojo finds out that Kayo has a relationship with the head clerk, Toya Shimada: in return for his recommendation for Shinnojo's position in the castle, he has demanded her body, and Shinnojo decides to divorce her. But when Shinnojo eventually figures out that Shimada merely took his pleasure with Kayo, he challenges the man to a duel.