A year after losing her husband, the mother moved to Tokyo from the countryside to live with her daughter and son-in-law. However, her daughter went back to Kyushu for a week for a class reunion, leaving the mother-in-law alone with her son-in-law. One morning, the mother-in-law saw her son-in-law's erect penis and, unable to contain her excitement, masturbated, while her son-in-law secretly took a picture of her with his smartphone. The mother-in-law, noticing this, pressured her son-in-law into sex and even let him ejaculate inside her. Furthermore, she had a threesome with her son-in-law's friend...