Koji, who lives with his brother and his wife, happens to see his sister-in-law changing clothes. His brother-in-law's wife, Chisato, has a voluptuous butt and big breasts that captivate and trouble him. Unable to bear her forbidden desires, Koji steals Chisato's underwear and begins masturbating with her, but Chisato catches him doing so. At that time, Chisato...