Rikako, who has been overprotective of her son who suffered a serious illness as a child, finds that even as an adult, her son has a lower mental age and relies on her for everything. Her husband worries and says, "Being too lenient isn't good either," but Rikako finds it hard to stop. One day, her son confronts her, saying, "My friends are having sex with their girlfriends. I want to have sex with you, Mom." Rikako, who ends up agreeing to perform oral sex on him, thinking, "Since we're family, we can't go all the way, but just the mouth is okay..."
