Rieko, who lost her husband at a young age, lived with her daughter and son-in-law. She got along well with her daughter's husband, Shinji, and they lived an ordinary but happy life. One day, Rieko witnesses her daughter and Shinji arguing about sex. Apparently, his daughter wasn't good at sex and kept refusing even when Shinji asked her to. Worried, Rieko talks to her daughter about it, but she doesn't listen to her. Then, by chance, Rieko happened to come across Shinji comforting himself. Surprised and shaken, Rieko takes an unexpected action. "My responsibility as my daughter is also my responsibility as her mother..." says Rieko as she grabs Shinji's penis. At first it was just a handjob...but then it was a blowjob...and then even sex... Rieko desperately resists Shinji, who is no longer stopping...