Reiko Sawamura plays Reiko, a married woman whose relationship with her husband has grown stagnant, leaving her increasingly frustrated and emotionally unfulfilled. Desperate for intimacy, she makes the forbidden decision to begin a secret affair with her son—a dangerous choice that risks destroying her family. Yet she resolves to carry this secret for the rest of her life. The moment her husband steps into the bath, Reiko's emotions surge uncontrollably. Her body grows hot with desire, and the brief 15 minutes she spends alone with her son become an intense, intimate ritual. During these stolen moments, mother and son explore their illicit bond, confirming the depth of their twisted passion. She etches each encounter into her memory, unable to let go of the forbidden pleasure they share.