It has been a week since his wife became pregnant and returned to her parents' home. Keitaro had been enjoying living alone again, but the quiet, empty house began to feel a little lonely. One day, his sister-in-law, Mio, came to visit. Desperate to escape his loneliness, Keitaro welcomed her warmly—yet Mio's true intention was to relieve her pent-up sexual frustration with him. Before he realized what was happening, Keitaro found himself in the bath with Mio washing his back. That's when Mio stepped in, saying, "Let me wash your back..."