Lonely every night due to her husband's work-related absence, Fumie begins indulging in self-pleasure to soothe her emotional emptiness. Her son Gorou, noticing her behavior, becomes increasingly tempted and starts secretly licking and sucking his mother's large breasts each night, masturbating to exhaustion. One day, Fumie wakes up and catches Gorou in the act. From that moment on, the two spiral into an obsessive, incestuous relationship, craving each other's bodies day and night.