Yuko is the fairy prince of a the Kingdom of Stars. Yuko was assigned by his father, King Mide, to protect the universe's most powerful objects known as the "Holy Star Crystals". One day, with out warning, Yuko's home was attacked by an evil sorcerer named Phantom in his attempt to steal the Holy Star Crystals. However, Yuko was able to send the crystals somewhere they will never be found by Phantom -- Earth. Yuko is serious and straight forward when it comes to his duties as a prince, and protector of the Star Crystals.. however, after meeting Yuki, his life changed and questions if he should return back to his kingdom, and say goodbye to Yuki forever once Phantom has been sealed away.

Yuko is, for the most part, pretty chill when it comes to the girls' normal everyday lives.. but when trouble arises, Yuko gets serious and wants the girls' complete focus when fighting.