Arion

(from ebookjapan):

Once upon a time there were... 3 brothers. They decided to divide the world into three parts and decide which part of the world each would occupy by drawing their lot.

The youngest brother, Zeus, who drew the first lot, became king of the Sky, and the second brother, Poseidon, drew the second lot and became king of the fertile Sea. The unlucky eldest brother, Hades, drew the third and worst lot. He was forced to become king of the dark Underworld...

Years later, Arion, a young, and promising, boy is kidnapped by Hades and raised for the day for when he goes to Mount Olympus to deal with Zeus once and for all.

Adapted into an anime film by Yasuhiko Yoshikazu himself in 1986, with the titled altered to Neo Heroic Fantasia: Arion. The tagline for the film was "There's an Arion in you!"