Riho and her husband have been married for a year and live with her father-in-law. Riho's sexual desire is very high, causing her husband to suggest that they both abstain from having sex for three weeks. Riho doesn't want to, but her husband keeps insisting, saying that sex will be extremely pleasurable after that period. Riho reluctantly agrees. However, after only a few days, Riho feels extremely uncomfortable down there. She tries to initiate with her husband but gets rejected. She can't take it anymore, so when her father-in-law is taking a bath, she puts on a small towel and goes inside, asking for permission to give him a back massage so she can play with his growing manhood. Slowly, she removes the towel and presses her large breasts against his back, using it to scrub him. Riho feels extremely aroused doing this with her own father-in-law while they still live together. And thus, the forbidden relationship between the father-in-law and daughter-in-law begins, as they always find a way to satisfy their desires even when Riho's husband finds out...