When Taria was first created in the aether, there was Rei and Chunari, the sun and the moon. With those two life flourished on the planet, and also death. As civilizations grew, the people began to believe in things. They believed in things so strongly more beings became present. Some people called them gods, some called them the kami. These beings embodied what the people believed in.
First came the being some came to know as Daichi, the embodiment of knowledge. The people around the woods and forests of the world grew Misumi or Mother Nature. Enyo grew from the people on the coast. The hard fishers who lived on the sea called upon him to give them stormless skies. The farmers had Minoru come to bless their farms and livestock, his gentle winds bringing life and seed to their fields. They also called upon Aiko, for good strong Earth for them to plant those seeds in. The women also called to her to bring healthy babies in their bellies.
More Kami came as people believed in more things. We've already met Kenichi as empires grew and fell, the lord of war. We've met Kentaro, who they call upon for single combat, and honor, may the power of his lightning strike down your enemy as you meet in combat. There were, of course, more, each of them embodying the different ideals and elements of the world and of the aether.
There was one Kami however, who wasn't quite of this world. She was brought about sometime, no one was quite sure when. Even Rei and Chunari weren't sure when this one happened into existence. This Kami was from the very universe itself. She had dominion over space and the stars themselves.
Eventually mortals in the realm discovered they could cultivate power from the aether and perhaps, one day join the kami in the Heavenly planes. Different mortals chose different auras to cultivate, schools and sects were formed and created to teach and help each other grow their power hoping one day they themselves might become a Celestial and join the Kami.