Libertia, a land of liberty.
Where people believed in freedom above everything else. And as a testament to their ways, they even offered said freedom to other races, namely, to demons. They even welcomed the demons in and were the first to do so.
And although humans and demons coexisted to some degree, it wasn't long before some influential nobles from the demon lands started establishing small colonies in the borders of Libertia.
Demonica hardly had any arable lands so they were always looking for ways to expand some more. Mostly to feed the people but also to gain more power. So when they saw the chance, they took it.