Reiko Nakayama is a full-time housewife who has been happily married for 20 years, with a son who has grown into a fine young man. Approaching her 40th birthday, she increasingly feels both her responsibilities as a mother and her lingering desires as a woman. One day, her son suddenly appears in her room wearing nothing but his underwear, and the sight awakens long-dormant desires deep within her. Stimulated by his presence, she finds herself unable to resist being drawn toward his crotch. Regardless of age, the feminine allure within her is now spiraling into a whirlpool of forbidden emotions.