Yurika, a mother, hears that her son, who left home to go to college, is depressed after being dumped by his girlfriend. She devotes herself to taking care of him until he cheers up, but seeing her out of the bath and in casual loungewear, in a vulnerable state, arouses her son. Unable to resist, the son masturbates in secret, and Yurika witnesses it... Mother and son soon become aware of each other as the opposite sex, and finally they can't hold back and cross the line.