Prince Theo (ティオ) is the main character in Doraemon: Nobita and the Legend of the Sun King. He's a hard hearted, as well as slightly tsundere person who wants to know how to be the great king.
Theo is voiced by Megumi Ogata in the movie.
Theo can be described as completely opposite of Nobita. He is harsh, reckless, somewhat selfish and has no caring personality at the start, as strength the only thing he believed that would lead him to become a successful king. He never even acknowledged (or morelike, doesn't even care of) Kuku loyalty and love toward him. When he met Nobita however, he start to learning about friendship and caring of other people emotion from him. By the end of the movie he has become a kind and caring king and he seems to accept Kuku feeling.