Yuriko gave birth to her son while she was a college student. Her son became a teacher, moved out, and started living alone. Today, they are going on a hot spring trip together for the first time in a long time. While Yuriko is happy with her son's growth, she feels that her life as a woman is coming to an end and is troubled by her own life. She takes off her blouse and skirt, lies down next to her son in her underwear, and whispers to him. Seeing her son's erection at the sight of his mother's naked body, she wants to be a woman. In a small, quiet hot spring inn, the real mother and son indulge in forbidden pleasure.