Momoko lives with her husband after their son leaves for college. One day, her husband brings home his long-lost brother, Tohru, whom he hasn't seen in seven years. Tohru's business failed and his appearance has grown rugged and wild, a stark contrast to his former self. When Momoko encounters Tohru in the bathroom late one night, she feels a long-forgotten stirring in her body, overwhelmed by passionate desire. Under Tohru's sensual touch, Momoko experiences pleasure for the first time, and gradually becomes addicted to their illicit affair. Soon, she finds herself eagerly waiting for him in the bathroom once again.