Pfft, who needs North Korea. There's no point in invading them. They have few resources and their country is of almost no strategic value to the West. Any potential value is more than equalled by S.K. and completely irrelevant next to Japan. Besides, eventually China will be a semi-ally too- everyone's scared of China, but the fact is that Western and Chinese interests are now and for the forseeable future highly similar. Taiwan is a touchy issue, but there's no way either side would allow a full-scake war over it.
China and Russia are all smiles and hugs, but sooner or later they'll come into conflict over something, and the West will sweep in, support China and isolate Russia. At this point, North Korea may have developed a nuclear device capable of damaging your hearing or possibly eyesight within a radius of 6 feet, and may have a firework powerful enough to just about get to another country some of the time; mst of the time if they use photoshop. This will scare Japan, who'll cry a bit, and we'll have to pretend we care some more. Meanwhile, they will go on starving and being shit. The end.