South Korea and Japan have experienced their worst deterioration of bilateral relations since 2012. What are the long-term prospects for this relationship? Will it continue on this negative trajectory or recover positively in the long term? Challenging the conventional view that supports the former conclusion, this paper argues for a positive outlook for the relationship in the long term. This is defended from a structural perspective relying on two long-term strategic trends for Northeast/ East Asia-the elevated uncertainty in the regional environment (due to North Korea and China’s strategic rise); and the rising strain on the U.S. military presence in both countries. In response to these structural pressures, South Korea and Japan will adapt and adopt strategies to defend their national security within a reformed U.S. alliance structure and strengthen strategic cooperation through bilateral and trilateral (with the United States) means.