Upon arriving, Bosse is told that his real name is Mio, and that he is son of the king and thus prince of the land. He finds a new best friend, Jum-Jum, and receives the horse Miramis from his father. However, he soon learns that not everything in this world is as wonderful as it first seemed. In the lands beyond that of the king lives an evil knight named Kato, whose hatred is so strong that the land around his castle is barren and singed. He has kidnapped several children from the nearby villages, and he poses a constant threat to the people living there.