The world is largely divided into northern and southern Kiboren. 1500 years ago, the Nhagas started a 'Great Expansion War' against other races to expand their territories. Conflict between the north people who needed farmland to eat grain and the nhaga who needed forests to hunt was inevitable. The kingdom of Arazi, founded by the legendary Rekkon 'the Hero King', was destroyed after hundreds of years of war against the nhaga. Because they are cold-blooded animals, the Nhaga, who could not live in the northern temperature, planted trees and created forests where they could live, and this forest that covered half the world was named Kiboren. Afterwards, Humans, Rekkons, and Tokebis, excluding Nhagas, lived in the North, where Nhagas could not come up, and Nhagas also lived in Kiboren, which became a maze that Northerners could not enter, and spent hundreds of years disconnected from each other.