While conceptually interesting, the manga itself is pretty shit. Don’t expect there to be any characters. Like at all. If there is one, he is an enemy fantasylander and dies quickly or is an ally fantasylander and serves to say, “Wow, Japan is so impressive.” The japanese themselves have even less characters than the fantasylanders, as bizarre as that sounds. Don’t expect any plot here either. There is no morally grey. Kingdom x is the bad guy oppressing y, so Japan helps y and in exchange gets the food to support themselves. Don’t expect real diplomacy — and certainly don’t expect the opposing fabtasylanders to be any form of competent, for even a minute. They don’t get a single win.
If you like watching a Japan military dominance wankfest, go read gate. It’s significantly better in all regards.