The only real problem I see in this is that South Korea already considers Japan to be the greatest threat to them and they've already been setting up their military to defend from Japanese invasion, so this will not help their relations and they'll probably keep ignoring Best-Korea at a time when they are becoming more likely to attack.
Really? They have China and North Korea nearby and they're most worried about Japan? Those guys really know how to hold a grudge.
Japan and the US and South Korea have a very strange relationship, yes.
...Well now that you mention it. Japan is a fanboy/lackey of the country that nuked them and occupied their country while South Korea is still more worried about Japan than the two countries that occupied Seul and tried to take over S-Korea the last time.
As for the Japanese military being used in attack... The way I see it the most likely place for them to invade (rather than simply get pulled into a war that someone else has started) would be that island cluster that they've been arguing about with Russia for decades. But even that is unlikely as a) they are much more peaceful these days. b) Starting a war that could turn into WW3 is not very smart and any country doing it would have to be really desperate and facing some kind of disaster even if they don't start a war.
Then again, they might go to Korea IF Best-Korea tries to attack again, because that IS a local hotspot where it would be in their interests to interfere. I can't see any likely scenario where they would actually declare a war and invade someone.
Maybe they plan to start defending their whaling ships from Greenpeace?
