Himeno Yuna and her fiance Nakade Yuzuru visit Nakade Tatsuo, who will be her father-in-law, for the first time. Tatsuo runs a guesthouse in the countryside and Yuzuru, who loves nature, wants to quit his job and take over his father's business. Yuna, who grew up in the city, was not very keen on this but this visit was also a way to scout the possibilities. At first glance, Tatsuo's impression of him was that of a tough-looking Showa-era man but he was a kind father who cared about his son and was a likable person who was also considerate of her, who would become his wife. That night, Tatsuo served her a home-cooked meal, drank alcohol and the conversation flowed and Yuzuru became completely drunk. Yuna was recommended by Tatsuo to use the guesthouse's hot spring facility, so she decided to go in by herself. Yuna, who loves hot springs, was enjoying the night view from the open-air bath when she sensed someone's presence. It was Tatsuo. Because the facility was small, it was a mixed bath. Although she was told that it would be a nuisance, she could not just refuse, so she carefully covered her body with a towel and went in together. There, Tatsuo begins to talk about his late wife. He says that she looks just like her. Her name is Yuko, which is just one letter different from Yuna's. He also says that maybe the reason his son Yuzu chose her was because he saw his mother in her. Moved, Yuna shyly accepts Tatsuo's request to see her from behind. He touches her hair, rubs her skin and things gradually escalate into a relationship with the drunk Tatsuo. The next day, tossed about by a mixture of emotions - guilt for having made a terrible mistake and excitement that she had never felt with her fiance... Yuna gradually becomes addicted to her father-in-law's charms and falls for him...