Satoshi's wife, Satoko, lost her husband at a young age and lived with her daughter and son-in-law. She got along well with her son-in-law, Shinji, and though their life was ordinary, it was happy. One day, Satoko accidentally witnessed an argument between her daughter and Shinji about sex. It seemed that her daughter was not good at sex and kept refusing Shinji's advances. Concerned, Satoko tried to talk to her daughter, but her daughter wouldn't listen. Then, by chance, Satoko caught Shinji masturbating. Shocked and flustered, Satoko took an unexpected action. 'My daughter's responsibility is also my responsibility as a mother...' Satoko grabbed Shinji's penis. What started as just handjob soon turned into fellatio, and then full-blown sex... Satoko desperately tried to resist the out-of-control Shinji...
