For the care of her father-in-law, Ayu and her husband Taro leave Osaka and move to Tokyo. One day, while Ayu is listening to the radio out of boredom, she comes across a news segment featuring a doctor claiming that female bodily fluids, especially vaginal secretions, possess anti-aging properties. Intrigued by this, her father-in-law becomes fascinated and eventually gathers the courage to proposition Ayu for sexual acts, setting off a forbidden relationship.