46-year-old Yuki Miyama is a housewife who boasts an ideal physique that's hard to believe she's the mother of two children. Her body is the result of 15 years of competitive swimming through college, and that dedication continues to enhance her allure. One day, she joins a gym to resume swimming after a long break—this decision ends up changing her life completely. Learning that the gym's shower facilities often become hotbeds for affairs, Yuki experiences her first infidelity with a gym acquaintance. After that, she becomes obsessed with sex with other men. As her affairs grow more frequent, rumors begin to spread within the tight-knit gym community, causing her distress. In pursuit of the perfect crime, she chooses to appear in adult videos, showcasing the sensual, athletic sex life of a mature swimmer's wife blossoming well past her forties.