In the story of incestuous adultery, "Mayuka" appears as a beautiful, kind, and gentle woman, yet harbors a deeply hidden erotic allure beneath her calm exterior. Living as a voluptuous wife by her husband's side, she also shows maternal warmth and care toward her stepson. However, she gradually begins to realize that her feelings for him go far beyond mere motherly affection. Even as she enjoys an active sex life with her husband, her emotions toward her stepson grow stronger each day. By night she is a wife, by day a stepmother, and secretly, the lover of her husband's son. Entangled in complex emotions, the story drives toward the moment when they finally cross the line.