Uhm yeah, ******** China on this one.
If I remember correctly, the first time that China started raising a fuss about the Senkaku islands was in 1972, after the US returned control of them to Japan, and only because a few years earlier a survey team suggested that their might be a huge-a** reservoir of "black gold" (oil) and/or natural gas beneath/near those five currently uninhabited islands.
Also, the Japanese formerly annexed those islands in 1895. The Chinese has been using the Potsdam Declaration as the basis for their claim, which basically said that Japan had to relinquish control of all islands except "Honshū, Hokkaidō, Kyūshū, Shikoku and such minor islands as we determine".
It should be noted that the Chinese (PRC) have occasionally
extended their claim to the entire Ryukyu chain (including Okinawa). So for them, it's a nothing more than a land grab for potential nearby resources.
Taiwan has a more legit claim than mainland China on this one. For them, the Senkaku Islands have been historical fishing grounds since the time of their ancestors (according to the Taiwanese anyway).
Given all this saber-rattling, I could see the United States being dragged into the fray if China trys to assert its supposed sovereignty over the Senkaku islands militarily.
As the Zen Master says, "We'll see."