Saying Japan or SK would fight is a weird way of putting it, since they would be following orders from the US, but I guess I agree with what you say. This scenario is an unwinable one since they also have not been cultivating a strong movement as was the case in Ukraine, where the CIA has bern training units since the Maidan Coup, and also Taiwan being so isolated and so much smaller. Plus China would have Vietnam and NK as allies which would difficult a lot the Japanese and South Korean armies.