After losing her husband, Miki Yoshii is supported by her concerned daughter and moves in with her daughter's family. Their peaceful three-person household takes a turn when Miki feels awkward witnessing her daughter and son-in-law getting intimate one day. She quietly distances herself, but soon begins secretly watching them have sex. The more she spies on them, the more aroused she becomes—eventually masturbating to relieve her growing desire. One day, when her daughter leaves for shopping, Miki is left alone with her son-in-law. Seeking excitement, she does housework without underwear, becoming increasingly turned on—until she can't resist any longer...