Sakae Fuji is 65 years old and lives with her husband and son. While her husband is away on a long business trip, she secretly begins a forbidden relationship with her son. One night, overwhelmed by pent-up emotions, she relieves herself through masturbation—only to be accidentally discovered by her son. From that moment on, he develops intense desires for her body, and the two gradually cross the line into a passionate, taboo mother-son relationship. On nights when her husband is absent, they meet in secret, indulging in a lustful affair that defies age and morality.