Koji, who lives with his older brother and his wife, accidentally sees his sister-in-law getting changed. His brother-in-law is fascinated by his sister-in-law Chisato's voluptuous buttocks and large breasts, which make him obsessed with her and torment him. Unable to bear his forbidden desire, Koji steals Chisato's underwear and indulges in masturbation, but Chisato finds him in the act. At that moment, Chisato...