After losing her husband, Kaori's health began to decline, prompting her to move in with her daughter and son-in-law. Despite her age, she finds herself increasingly aroused by the presence of her young son-in-law. One day, while her daughter is away on a business trip, Kaori overhears the couple having sex and becomes so excited that she indulges in masturbation alone. That night, her drunken son-in-law returns home and collapses in the living room. When Kaori tries to help him to bed, she notices his erect penis and is overwhelmed by a new, forbidden desire.