As her son enters puberty, he becomes increasingly drawn to his mother Yumi's breasts. She habitually goes braless, adding a secret allure to her daily life. Noticing her son's gaze, she playfully teases him by swaying her chest, deepening the bond between mother and son. However, one day, the boy's adolescent desires finally reach their breaking point. Yumi's voluptuous bust becomes the catalyst that stirs his emotions, sparking a forbidden new relationship.