Humans thought they were unique, that they were the best adapted animals. They were wrong. For just as long as humans have lived, so have the Ucari, creatures that take the form of animal and man. The Ucari lived their lives staying unknown to the Humans, in fear of how they would react to creatures that were different. Of course every now and than an Ucari would be seen shifting from man to animal, and so legends of creatures like Werewolves were born.
The peace was kept until a radical Ucari group showed the world what they were, a group that wanted the Ucari to be known as the most advanced creatures on Earth. War broke out between two sides that, those who attempted peace were forced to fight or die. A war that lasted as long as forty years, and ended in a disaster that swept the Earth.
It's been thirty years since the war ended, the Humans are thought to be extinct, while the remaining Ucari live scattered in an apocalyptic world. No laws, no economy. Only Survival.
(The prologue explains more<3)