Speaking of population, would something about 9,000,000 be okay for me?
Again, going off the ww2 Japanese pop, the additional population would come from the Birthing Rites edict that the first Golden Emperor put in place to recover the population after the Age of Strife.
It literally put quotas for certain households to have so many children and so forth in a way that the nation could still support all of them (some what)

It can also be seen as the reason why Fusan society is a bit... [i]salacious[/i] compared to other nations which is still very seeable today, even in the military. Anyone who want to know more about that, PM me or wait :P