Originally the Korou were humans with a Kekkai Genkai that allowed them to take on traits of animals and use their abilities temporarily. At this time many didn't know what a Kekkai Genkai was and when it was demonstrated in front of ordinary people, many grew fearful and attacked them. Once there they began to settle down, continuing their former way of life, as beasts, and humans. Over time the Korou began to call the world, Tenchikaimei and have lived in peace for the most part since they left the Shinobi world.