In the face of FTA developments across the world, China, Japan and Korea have all made serious considerations towards various regional cooperation mechanisms and made efforts towards negotiating for frameworks that contribute to their respective national interests. In East Asia, particularly after the conclusion of the China-Korea FTA in 2014, China became even more actively involved in the push for negotiations over the RCEP and China-Japan-Korea FTA. Other negotiations not only do not conflict with the TPP, at the same time, Japan also participated in negotiations over the TPP, RCEP and CJKFTA. Although in terms of traditional gains, CJK FTA may yield more benefits for Japan than the TPP, Tokyo's geopolitical considerations for the US-Japan alliance, East Asia leadership and regional security seem to continue to override the pursuit of economic interests. This article examines the reality that Japan has become a key variable in cooperation in Northeast Asia and seeks to analyze its potential development.