Young and pure mother Haruki and her son Shiro share an unusually close bond, appearing more like a couple than mother and child. Their familial connection is strong, and they’ve always shared everything—yet as Shiro entered puberty, conversations about sex became increasingly avoided. One day, Haruki is informed by Shiro’s homeroom teacher that he brought an adult video to school, causing an incident. Deeply troubled, Haruki decides to personally teach her son about sexuality—using her own body as a guide. Initially hesitant, Shiro gradually becomes captivated by the sensation of his mother’s lips and her soft, firm breasts. Through the forbidden act of losing his virginity to her, he experiences a woman’s body for the first time. A unique bond between mother and son intertwines with innocent curiosity, evolving into a new, intimate relationship.