While her husband is away, Rika becomes addicted to forbidden sex with her brother-in-law Kentaro. As their relationship cools, Rika resists Kentaro's advances but gives in to him. Her reason is disturbed to the point that she thinks this is an unforgivable act. Her attractive breasts are kneaded wildly, and she and her brother-in-law have intense sex many times from morning until night. They spend the best time together, desiring each other, and a sense of guilt and euphoria mix violently in their brains.