IFast forward to 2021 present day, away from the "colonial days" which every country around the world is guilty of including China (e.g. of Taiwan not long ago which it is trying to annex again) and the other countries you mention, not to mention them also being nuclear powers....
if a Filipino or Indonesia fisherman cannot even fish in his own waters, or a Taiwanese resort owner and guide can't receive ferry loads of tourists to his island because they're being surveilled and overlorded by Chinese naval vessels from a few kms away, what do you expect Japan, Taiwan and South Korea to do in such a region? Of course they are going to look outward for the most powerful allies
