After losing her husband, Machiko started living with her daughter and son-in-law. One evening, the son-in-law, who had been coldly treated by his wife, was caught by Machiko masturbating in the toilet. Machiko got excited and masturbated under the covers but was seen by the son-in-law instead. On Sunday, the daughter went shopping alone. Mako witnesses her son-in-law masturbating again. Confused Mako. Her son-in-law confesses his feelings to her. Then, unable to hold back their lust, the two have sex. From that day on, their taboo acts gradually become more intense. Mako is tormented by guilt, but succumbs to her son-in-law's passion and ends up having sex with him again...
