Mio in the Land of Faraway(1987)

They're two best friends, a million miles from home. On an incredible adventure, beyond the boundaries of space and time. In a place called...

Under the watch of his unkind realtives, lonely Bosse's luck is changed when he is sent to the land where his real father is the King. In that country, he sets out on a quest, together with his new friend, to destroy the evil Knight Kato.