I wonder what the Japanese government's internal timetable of splitting from the US looks like. Historically Japan has been very sharp on sensing which way the wind is blowing and where the smoke's coming from.Biden managed to unite Russia with China.
Trump will manage to unite Japan with China.
Where is that meme of Xi doing nothing and winning?
I wouldn't be surprised if one of their contingencies around AR is; if China looks to be the overwhelming winner / US unable to respond then we inform the US that "all your Japanese base are belong to us", if the US is in a stronger position after the event then we stick with status quo.
This would follow their tradition of kicking someone while they're not looking and ingratiating themselves to the (new) powers that be.
South Korea again would be the slow kid on the block; unless China actively guides them through diplomacy, I would expect SK to be in a state of confusion and infighting for several months until it becomes blindingly obvious what the right choice is, and even then you will have US-Yoon loyalist fringe groups that refuse to accept reality.