Mao, a young wife, visits her parents' home to nurse her injured father-in-law. Having lost his wife and not had any experience with women, her father-in-law becomes aroused by the gentle nursing she gives him and pushes her down on the futon. Mao, who is not satisfied with her sex life due to her husband's busy work, is toyed with by her father-in-law's forceful fingers and, although she hesitates, accepts his erect cock in a consensual family affair. Next to her sleeping husband, Mao's father-in-law creeps up to her body, and she climaxes while suppressing her voice so her husband doesn't notice, in a forbidden night-time creampie sex session.