The daughter and son-in-law wanted to save money to buy a house, so they came to live at their mother-in-law's house. Reiko used to be a photo model, and she didn't know that her son-in-law was a fan of hers. One day, Reiko accidentally discovered that her son-in-law was watching a movie with an actor who looked very much like her, surrounded by photos from when she was a model. He used her photo to masturbate! Her son-in-law's big cock made Reiko unable to take her eyes off. It turned out that because the cock was too big, it hurt Reiko's daughter, and it had been a long time since her son-in-law had had sex, so he had to "deal with" it alone. Feeling sorry for her son-in-law, Reiko decided to offer to "take care" of this big cock on his daughter's behalf. Before Reiko's invitation, plus the fact that he had endured for so long that he couldn't resist anymore. Since then, the two have continuously secretly fucked each other every time they have the opportunity, secretly maintaining this wrong relationship...