WW3?
I don't think any war in that region will happen soon. there is a status quo involved that everyone is more or less happy to continue because the alternative is worse. Normally when tension increases on the North Korea side it's because they want something and they try to use threat tactics to bring everybody back to the table. South Korea and Japan complaining is a good weapon for them because the US is likely to negotiate something. China too they don't want a war on their borders even if they don't particularly like Japan they have no real reason to go to war with the Japanese. It wouldn't benefit them and China tends to be much more pragmatic than it's neighbours. They usually only get involved when they have something to gain. Baiting the US into a war on their border doesn't do anything.
China in more recent years have become frustrated with North Korea and it's threats along with a new leader who is young and egotistical. North Korea probably still isn't going to disobey China but they don't listen as much right now and that likely has a lot to do with Kim Jong-un and even some of the elite of the country dislike him. It seems to be much of a show lately an important party congress is coming up so it seems to be a show of power more than anything else for the people in the party to see how strong he is as a leader. China has also backed sanctions against North Korea because of them breaking agreements on nuclear weapons.
China and the US have some territorial issues about where their military can operate and build bases but again there isn't a benefit to going to war over that for either side so they won't. Russia seems to care less and less about North Korea it's not a priority for them anymore they are busy with trying to reclaim some of the old Soviet Union and with the Middle East where they are jostling for influence and position with the US.
I don't think any of the recent tensions are anything new nor a real concern going by the current political climate and evidence from how these issues were dealt with in the past. North Korea is having food issues again and requires aid so they'll make a bunch of threats and then be offered aid in return for reigning in their missile tests and threatening rhetoric.
I'd love to hear your views on the region.