I don't think Japan or South Korea will be in too much danger much longer. My sense is that both nations can (and should) get nuclear capability in a few years, which will provide them the deterrent they need to keep China at bay.
The other countries ... meh.
And if China wants to shoulder the burden of patrolling those waterways, let them spend their money on that.
The other countries ... meh.
And if China wants to shoulder the burden of patrolling those waterways, let them spend their money on that.