Just a thought for disputed territories....
Why not treat disputed lands as a sort of international resource? Either Japan or China could cede the islands to the other party, but with a treaty that provides for international access. The Svalbard islands offer a useful example of how this might work. While the islands are technically governed by Norwegian law, Norway places no restrictions on who can go there.
Wikipedia reports: "Norway grants permission for any nation to conduct research on Svalbard, resulting in the Polish Polar Station and the Chinese Arctic Yellow River Station, plus Russian facilities in Barentsburg. The University Centre in Svalbard in Longyearbyen offers undergraduate, graduate and postgraduate courses to 350 students...with Norwegian and international students equally represented." The archipelago is also home to the Svalbard Global Seed Vault,a priceless genetics resource of world significance.
Something like this sounds a whole lot more pleasant than sabre-rattling and ominous predictions of unnecessary regional wars.