If the answer is 'yes' then what's the point of having Japan at all? Nobody in the region is going to have a navy capable of defeating the IJN anyway, and they're unlikely to be able to stand up to the much stronger than OTL East Asian land powers successfully without allies anyway. Why not just leave the land blank?
Not saying that they should automatically become best buddies with me, or Frigid or anybody else in the area, but they are supposed to be a major power, if they're anything like OTL. Having them be a diplomatic nonentity would be ridiculous, and considering their strategic position, they'd certainly at least try to play the mainland powers off against one another, as Britain historically did in Europe.
My point, pretty much, is that if NPCs aren't going to do anything, then they shouldn't be in the game. If anybody ever followed the Lords of Ether story debate on SB.com, one of the things that made it awesome was that the NPCs actually did stuff, and that they were powerful enough in their own right to not just be punching bags for the players. I'm not saying that these NPCs should be that active (I presume our GMs have other things to do), but they shouldn't just be inert lumps that only respond to PC actions.
I also realise that having said that, I'm probably going to get my arse kicked by mongolian mind flayers or something.