Xuu and Guu were once the same being, the first guardian and child ever of the mother Gaia, manifested through emotions, magic energy and substances of the nature, he had no distinct gender, within the centuries he observed all the living creatures living upon his mother gaia, feeding from the products of its soils and sea, developing some kind of love and compassion for these beings, focusing specially on mammals, some of them adapted to the life at sea, some of them in trees, some of them in the air, underground or on two legs, there was a certain branch, the favourite one of Kuu with a peculiar erected body posture only using their feet to stand.

The humanity managed to become the most dangerous predator of the earth, increasing their population and extending it to every continent of the planet, their destructive behaviours alarmed the will of Gaia, forcing him to become a corporeal being, manifesting in an humanoid figure among the human civilization.

Kuu could no longer tolerate the destruction as a byproduct of human progression and wanted to completely wipe humanity from existence. It used the powers gained from nature purely as a tool for chaos until some members of an ancient clan decided to seal him with the three sacred treasures, right before being sealed, the will of gaia split himself in two beings, one of them was sealed and the other one managed to escape to the outer space, sleeping for thousand of years floating through the vast nothingness.

One hundred twenty years passed, a human called Remus found some kind of strange crystal with a K carved deeply on its hard texture and a tiny little being sealed inside, it seemed to make some kind of strange reaction with the magic energy, absorbing it closely instantly on contact. Remus had a hunch and tossed a enormous quantity of mana accomulated into an orb; Suddenly, the majin crystal exploded, shattering into small sharpened crystals and releasing the creature inside.
The counterpart called Xuu felt the energy of his other half, awakening him from the hibernation within the outer space, feeling the urge to become Kuu, the will of Gaia again to protect the mother earth from the pollution of the mankind.