Sayako lives with her husband and son. She still has a good relationship with her husband, and they continue sneaking affectionate moments whenever their son isn't looking. However, lately her husband's cock has become soft, and although she's still aroused, she can no longer achieve satisfaction. Sayako hides this frustration, seeking relief through masturbation late at night. One day, her son discovers her masturbating and says, "Dad's soft dick can't satisfy you anymore, can he? Let me make you feel good with my cock," tempting her. From that moment on, she begins secretly meeting her son behind her husband's back...