Nanaka Takanashi is the mother of Shūsuke Takanashi and the adoptive mother of Nao Takanashi, married to Shūji Takanashi. She consistently perceives her son Shūsuke as a perverted child. On their first date, her husband Shūji took her to a pornographic movie. Along with her husband, Nanaka reluctantly revealed to Nao that she is their adopted daughter, explaining that Nao's biological parents—close friends of the family—died in a car accident approximately ten years prior. Nao survived the accident but suffered memory loss. The couple adopted Nao after Shūsuke urged them to do so, vowing to become her big brother and protect her.