I think Imu is a king of a kingdom somewhere, just like Lili was the King of Arabasta and the Doflamingo’s ancestor was the king of Dressrosa and Nasujuro’s ancestor was probably the Shogun of Wano.
probably all of the first 20 kings and their kingdoms are human kingdoms
Because I have a theory that the other races all have human ancestors anyways, but they were genetically modified to have descendants with super abilities by ancient civilizations