Several years into her marriage, housewife Yumi decides to start a cooking class at home. She invites instructor Tamura to conduct lessons for housewives. One day, after the students leave, Yumi and Tamura are alone together. She ends up confiding in him about having been in a sexless marriage for the past year due to her husband's lack of interest. As they talk, her pent-up frustration grows, and Yumi impulsively sleeps with Tamura on the spot. That night, Tamura suggests, "How about giving your husband some stimulation?" Yumi shares the idea with her husband, leading to the birth of a new relationship dynamic between the three of them.