Korea and Japan are two key allies of the United States in East Asia. These two countries are “window models” of postwar democratization and economic advancement in a free world. Sustained security provision of the United States to these two allies during and after the Cold War period provided a stage for upgrading their global status as well as enhancing the quality of life of the people of the two countries.

For the past 43 years, since Korea and Japan normalized their relationship in 1965, cooperative ties between the two countries have leaped forward. In 1965, the number of people visiting the other country was approximately 10,000. In 2006, 4.46 million people visited each other, which means that more than 10,000 Japanese and Korean people have been entering the two countries in a single day. In 1965, bilateral trade between the two countries was only $240 million. In 2006, trade between the two was recorded at $78.5 billion. The “Korean wave,” or hallyu, is so widespread that Japanese housewives and youngsters are fascinated by Korean movie stars. Increasing number of Japanese style izakaya are found in Seoul.1 These are living examples of deepening ties between Korea and Japan.

However, frictions between the two countries have never faded away. We find more, not fewer, instances of history-related frictions since the mid-1990s. History textbook controversies, Yasukuni shrine visits, and Dokdo/Takeshima disputes galvanize both the Korean and Japanese publics. Anti-Japanese sentiments in Korea are not necessarily on the rise, but reactions to the Japanese provocations are becoming intensified (Park 2008b, 5–30). Also unlike the Cold War period when both Korea and Japan antagonized North Korea, the two countries have acquired diverging perceptions of the North Korean threat during the past decade. This laid the groundwork for submerged but potential conflict.

There is no doubt that cooperation has increased and deepened during the past few decades, but frictions persist. What is going to happen in the future of the Korea-Japan relationship? Is cooperation between the two promised? Or is conflict unavoidable? In a word, where to from here? These are profound questions that this article tries to address.

As for the future of the Korea-Japan strategic relationship, opinions are divided and empirical realities are mixed and complex. Assuming that theories can work as a guiding light to navigate through the unknown future, I would like to address this puzzle from an analytical point of view. I will apply contemporary international relations theories—realism, liberalism, and constructivism—to the future of Korea-Japan relations and interpret mixed signals with a prism of theoretical perspectives. After reviewing both optimistic and pessimistic views drawn from diverse perspectives, I would like to draw out a synthesis that stands on cautious optimism.