Mother Kana and her only son Yuzuru live an ordinary life, which takes a dramatic turn when Yuzuru discovers his mother's intimate affair with her lover. Witnessing the act shakes Yuzuru deeply, stirring emotions he cannot ignore. Seeking to understand her son's inner turmoil, Kana decides to guide him through sexual education using her own body. What begins as a mother's duty and affection gradually transforms their relationship into something far more intimate and intense.