Widowed Yumi raised her son Nobuyuki on her own. Though she felt conflicted about her son becoming involved with women, one day he confided in her about his struggles with premature ejaculation and inability to satisfy his partner. Determined to help, Yumi resolves to give her son sexual training. She tries stimulating him through handjob and blowjob, but his condition doesn't improve. Eventually, Yumi decides to use her own body to teach him the art of sex. The story portrays her actions, driven by maternal love and responsibility, blurring the lines between parent and child.