And, yes, this is about China. KJI seems almost anxious to get rid of his nuclear weapons, and ballistic missiles really aren't that useful for anything else: Other WMDs are crapshoots at best with chemicals or bioweapons standing a real chance of ending up blowing back to the Korean Peninsula, and you don't mount conventional weapons on ballistic missiles.
China, on the other hand, has a fair number of nuclear missiles, has been a wee bit belligerent to Japan in the past, and is very, very interested in Taiwan- a country that could easily be put under a Japanese BMD shield. Not that anybody will say anything concrete to that effect. They'd be idiots to do so. But just keep it in mind.