This is a very dangerous game of roulette in which a mentally deranged leader of a piss poor country is playing. Back a few years ago, Russia threatened invasion of North Korea if it didn't change it's course. Both China and Russia supported North Korea during 1950's Korea war that cost the lives of tens of thousands of American soldiers.
In the geopolitical world of chess both China and Russia have a natural interest in that part of the world not only geographically but economically. You would think mega-supowers would be placing extreme pressure on North Korea to cease and desist now, but that hasn't occurred since missile testing has continued non-stop.
Japan itself, use to be a world super power but hasn't had an offensive military since the closing days of WWII.
I am concerned the stalemate may require US involvement and things could get very nasty, very quickly.