Grassblades takes place in a fantasy-world whose closest real-world analogue would be medieval (15th-17th century) East Asia, with many smaller noble houses struggling for control over the land. I haven't gone much into the political and military conflict, but the society is structured such that there isn't one, all-power ruler - there is no Emperor, no High King, nothing like that - and no nation as such. The land is divided up between various noble houses who each control certain areas, and occasionally come into conflict about them.
Here and there are royal houses, who title themselves king and queen, rather than lord and lady, but it's mostly just a title-change.
The world isn't supposed to be a direct fantasy equivalent to any one specific nation's history, so all locations are completely fictional.
It's a world where spirits and demons and gods are real, but not everyone believes in them. Some people believe in gods, but think ghosts are fictional - the same way some people in our world believe in the gods of their various religions, but think belief in ghosts is silly. There are true believers, convinced sceptics, and people on every step of the scale between.