Overwhelmed by work and household duties, Masako suffers from severe shoulder tension. One day, she sees a flyer for a massage service and calls in a therapist. The man who arrives is an erotic masseur. As he works her body with oil, Masako experiences pleasure so intense it nearly makes her pass out. Then, claiming it's "internal vaginal massage," he penetrates her, awakening her long-suppressed desires. Her lust grows uncontrollable—soon, she turns her attention toward her own son's body.