Seoul’s voice with Beijing is stronger in concert with Washington’s and Tokyo’s than it is solo
Moreover, the belief held by some South Koreans that there is no cost to bad relations with Tokyo is wrong. Two major new initiatives in East Asia-the Quad (Quadrilateral Security Dialogue) an alliance that unites Australia, India, Japan, and the United States, and Japan’s “Free and Open Indo-Pacific” strategy-moved forward without South Korea in no small part because of its poor relations with Japan. Joining together with Tokyo and Washington would not just bolster South Korea’s policies to deter North Korea but also serve Yoon’s aspiration for South Korea to play a pivotal role in everything from supply chains to development assistance-areas in which Seoul’s two allies are key players.
For Yoon, improving trilateral relations with the United States and Japan would provide the strongest possible foundation for dealing with China
For Kishida, trilateral cooperation would be good for “realism diplomacy,” as he described his foreign policy approach in a speech at the Shangri-La Dialogue in June.