A group of uninhabited islands south of Okinawa have the potential to increase tensions between China and Japan. The Senkaku island group is subject to overlapping claims from China, Taiwan, and Japan:
Japan reports that, for the third time in the past 18 months, Chinese warships have been spotted south of the Japanese Island of Okinawa. This time, it was two Chinese submarines, running on the surface. That had never been seen before, in the area near the Senkaku islands (which are claimed by China, Taiwan and Japan). The Senkakus are eight uninhabited islands, which in the past were only used occasionally by fishermen. The Senkakus are 220 kilometers from Taiwan, 360 kilometers from China and 360 kilometers from Okinawa (which is part of Japan).
[. . .]
Five years ago, a Chinese oil drilling platform, in disputed waters halfway between China and the Japanese island of Okinawa, began producing natural gas, despite ongoing negotiations over who owns what in that patch of ocean. The Chinese spent two years building that platform, in waters claimed by Japan. A second platform was later built, as well as an underwater oil pipeline for both platforms. China regularly sends groups of warships to patrol the area, to underline their belief that this bit of water is under Chinese control. Japan would probably win any naval war with China, but since China has nuclear weapons, and Japan does not (at least not right now), such a war could go seriously against Japan. This has been brought up in Japan before, and it is feared that the issue may lead to Japan secretly, or openly, building nuclear weapons (which it could certainly do, and quite quickly.)
I’m certainly hoping that this is just speculation on the part of Strategy Page (the bit about nuclear weapons), as territorial disputes over islands do have a way of getting out of hand (see Falkland Islands, for example).