Kimijima Mio lives happily with her husband and father-in-law. Her father-in-law is 80 years old and is not in good health, so she is always there to take care of him. Her father-in-law is a very good person, so taking care of him is also Mio's happiness. Not only that, there is a secret between the two that cannot be told to her husband. Mio takes care of her father-in-law from A to Z, even taking care of his "needs". But she does not cross the line, she only helps him with her hands and mouth, and one time when she went to the market, her father-in-law fell because he wanted to go to the toilet. Her husband saw this and immediately wanted to put him in a nursing home so that he would be safer. He also quickly booked a place for him without asking Mio and her father's opinion first. Her father-in-law's stay here is only four days. Mio realized that she wanted to be with her father-in-law more than ever, she wanted to have more memories with him, and then the two crossed that final boundary. The two of them made love to each other crazily over and over again, creating many beautiful memories together in the little time left...