Yusuke's classmates tease him about being a virgin and he spends his days feeling depressed. His mother, Yuka, is genuinely worried about her son and keeps trying to give him kind words to help him gain confidence, but it's no use. Unable to bear it any longer, Yuka offers her body to her son and becomes his first sexual partner. She starts sex education for her son's sake, but Yusuke becomes dependent on his mother's body and desires it...