Yurika, who became pregnant during her student days and raised her son as a single mother after divorce, finally takes him on a hot spring trip with money he saved from his part-time job after entering university. Her son, who harbored feelings for her as a woman, confesses his love and advances on her. Yurika resists, calling out that it's wrong for them to be intimate as mother and son, but as he licks her nipples and caresses her pussy, she finds herself experiencing sensations she hadn't felt in a long time, despite her initial resistance. Lost in the unfamiliar pleasure, they give in to each other's desires, engaging in a forbidden incestuous affair that culminates in repeated climaxes.