37-year-old Asako has lost her husband and is observing his third death anniversary. On this day, she reflects on how she wants to exist as a woman. Her son Koichi notices the change in her expression and senses the shift in his mother's heart. When he asks, "Mom, aren't you lonely without Dad?" she replies, "What are you saying? You, of all people..." Yet, Asako begins to become aware of herself as a woman. The day after the memorial, her brother-in-law Taro visits. Noticing his gaze, Asako becomes conscious of hidden emotions within herself and finally surrenders to Taro. In the moment, she whispers, "I'm sorry... I'm so sorry." Meanwhile, Koichi returns home from school and senses something strange about his mother. He confronts her, and upon learning the truth, becomes deeply shaken. He declares he must examine the body his uncle has defiled. As he touches his mother's body with anguished tenderness, he realizes his own arousal and erection, then flees the room in distress. Noticing this change, Asako goes to Koichi's room and gently takes his large penis into her mouth. Awakened as a woman, Asako repeatedly masturbates to calm her burning body, but eventually can no longer resist craving Koichi. And so, she makes the choice to open the door to forbidden desire...