Since the current economic downturn, the trilateral relations between China, South Korea and Japan has improved steadily. They are now pushing forward with their own regional cooperation agendas. First, there was the joint development of undersea resources in the disputed zones between China and Japan, (here) then the study of the "East Asian Community" concept (here), and now the Trilateral Summit on DPRK relations. (here)
Historical and regional geopolitics will prevent a formation of an Asia EU as suggested by the new Japanese Prime Minister Yukio Hatoyama. However, that region is also home to 16% of the world’s GDP, thus any attempt to further cooperation should not be viewed as a zero sum game. The PLAN's visit to Korea and Japan and the associated training exchange can be viewed as an example of this regional cooperation. Hopefully, the diehard nationalists from all sides will understand.
China Defense Blog