With his wife nearing her due date and their baby almost here, Shoko, his sister-in-law, comes to visit. Sex-starved and pent up, he slips away to masturbate, only for Shoko to catch him. He manages to play it off, but with her own husband living away for work and her needs going unmet, Shoko uses what she saw to toy with him. Before long, the thrill of sneaking around wherever they can sweeps him up too.