While his wife was away on a trip, Goro was struggling with unfamiliar housework. Then, his wife's sister, Rie, came to help with the housework. Goro, who couldn't even clean properly, happily welcomes Rie, but something seems off. Not only does she get too close, but the sensation of her forced large breasts makes his rationality melt away. Goro, who can only be taken aback by the proactive Rie, flees to the bathroom... but he can't escape Rie's clutches...