Sayo (30) is a married woman in her fourth year of marriage—youthful-looking yet sexually assertive. She fell in love at first sight with a man she met at a restaurant, approached him herself, began dating, cohabited, and married him three years later. Hoping to have children, she quit her job to become a full-time housewife, but pregnancy never came, and marital sex gradually decreased. Fearing their relationship would turn into nothing more than a shared household, they planned a hot spring trip to rekindle their bond. This journey serves as a rehearsal for that trip. Encountering a stranger for the first time, she gives in to his advances. Her nipples harden with arousal as she's vigorously taken from behind by the window, writhing in ecstasy.