I wonder where TWN would stand if fighting did break out. It'd be confusing, since both TWN and JPN are US allies. But TWN opposes JPN's claim of Diaoyu (and its own claim of Diaoyu is the same one as the PRC's)...:dbananaWell for a start it certainly doesn't want to but if things suddenly got worse, it would be left with little choice, especially if its key national interests came under threat.
The JPN move to "buy" the islands from its "private owners" (it is never mentioned who they are) is a grand master stroke.
Without deploying a single military personnel, this seemingly civil gesture has brought PRC closest to losing its composure and show its hand.
If they manage to provoke the PRC into aggressive military action with a civil gesture, PRC will then be proven to be the aggressor and thus give US the perfect excuse to intervene.