-On Topic-
Taiwan joining the Japanese Side would be a game changer in Senkaku issue, if I was China war planner. I would plan an incursion thru Taiwan as a logistic base, now, with Taiwanese signing this agreement, I very much doubt Taiwan would allow China to use its Keilung Port to do something like that. PLA Navy currently do not have underway refuelling technology for their ship, meaning they need to march thru Senkaku via North Eastern China, which add some 200 miles to their journey. By the time they reach senkaku, their station time would have been cut in half
On the other hand, Japan can refuel their own ship in Ishigaki, that seriously favour the Japanese. Not to mention now Senkaku is now a money making ground for Taiwan as well. No guarantee if China retook it, it will allow Taiwan to share the resource (I don't really think it's possible after the Taiwanese flip the Chinese the finger. It will not come as a surprise if I saw news report Taiwan and Japan form a defensive allied on Senkaku. Which make the situation harder for China.