Humans fight to protect their land from invading demi-human tribes in relentless battles. As his world is engulfed by intense warfare, Kai, a village boy from Lag, joins the fight to defend all he knows. After Kai’s comrades fall one by one and he’s injured, he suddenly recalls memories from another life. A fantasy tale unfolds as a village boy explores a world of magic, mystery, and heroism.

The story is set in the galaxy located near the center of the universe.

There are Planet Aernia (a planet for Heroes) and Planet Orbs (a planet for robots), governed by Orbiton, in this same galaxy.

Various countries are present in Planet Aernia; they are, Volculm (volcanic country of fire), Zylan (oceanic country of water), Elvan (green-rich country of forest), and Aleum (celestial country of clouds).

Antania, is a nucleus of all the present countries. It has an academy that fosters Heroes.

Under the reign of the Governor General, Antania upholds a national policy to train Heroes to prevent Planet Aernia to be infringed by the Dark Desire.

Heroes are not only the reliable source of battle who have special abilities to freely use the battle discs, but also a symbol of unfailing justice.

Spaak, a very powerful and respected G.C. (Great Child) offers his position to a young boy named Bucky who has the dream to become the ruler of the world. In order to become a true G.C. to protect his land from animals that have gone haywire, he must cross the twelve countries and defeat each G.C. guardian who are ordered by the G.C. leader Hail to stop him. Kai and Pinky who are also G.C. follow Bucky on his journey to make his dream come true.

Although he may appear rough-and-tumble, Jiro Azuma's compassionate side emerges when it comes to the furry critters he can communicate with. But Jiro's soft spot for animals gets him in major trouble when a suspicious stray cat fuses with him, granting him exceptional power but also dragging him into humanity's hidden battle against powerful Japanese spirits, mononoke.