Sayaka and Koji have raised their eldest son and daughter, both of whom are now adults and married. Their eldest daughter, in particular, is married to Satoshi, and the couple lives together with Sayaka and Koji in a dual-household setup. The families enjoy a harmonious relationship, and daily life proceeds peacefully. However, Sayaka and Koji's sex life has lost its former passion. While Sayaka accepts this, a lingering sense of dissatisfaction remains deep within her. One day, Satoshi and Sayaka are left alone at home. Drinking alcohol from midday, Satoshi—being a light drinker—passes out first, leaving the body of a man past thirty lying unconscious before Sayaka. In that instant, Sayaka's heart begins to stir once again.