Princess Knight, also known as Ribon no Kishi, is a Japanese manga series written and illustrated by Osamu Tezuka. This manga follows the adventures of Sapphire, a girl who was born accidentally with the blue heart of a boy and the pink heart of a girl. She pretends to be a prince to prevent the evil Duke Duralumin from taking over the kingdom through his son, Plastic. The gender-bending main character was inspired by the all-female musical theater group Takarazuka Revue in which women performed both female and male roles.