Princess Knight

Princess Knight (リボンの騎士, Ribbon no Kishi), is a Japanese manga series written and illustrated by Osamu Tezuka. It was originally serialized in Kodansha's Shōjo Club from 1953 to 1956, later collected and released into two tankōbon volumes, and three other serializations between 1958 and 1968, which spawned many types of related merchandise. An anime series was produced by Mushi Production, which aired on Japan's Fuji Television from 1967 to 1968, which was later dubbed in the 1970s.

Plot
In the kingdom of Silverland, Princess Sapphire was born and raised as a male to inherit the throne (as women are not eligible to do so). The deception was to prevent the evil Duke Duralumon from inheriting the throne.