South Korean President Lee Jae-myung visited Japan from August 23 to 24, ahead of his summit with U.S. President Donald Trump in Washington, D.C. The timing is notable, marking an unusual decision for a South Korean president to meet with the Japanese leadership before engaging with the United States. This move reflects Lee’s pragmatic foreign policy approach, aimed at balancing relations with neighboring countries while strengthening the Japan-South Korea-U.S. trilateral framework.
Although a liberal leader who has consistently underscored Japan’s’ responsibility for its wartime atrocities, Lee signaled a forward-looking diplomatic agenda with Japanese Prime Minister Ishiba Shigeru, whom he even said felt like a “very close friend.” The summit resulted in the publication of an official joint statement for the first time in 17 years.
The Kim-Obuchi Agreement
The foundation for today’s bilateral relationship was laid when South Korean President Kim Dae-Jung and Japanese Prime Minister Obuchi Keizo met in October 1998. They issued the Kim-Obuchi Joint Declaration, which pledged to build a renewed Japan-South Korean partnership aimed toward the 21st century. Both countries acknowledged the “tremendous damage and suffering” Japan caused to Korea during its colonial rule, while pursuing reconciliation and future-oriented cooperation between the two nations.
The 1998 Joint Declaration highlighted various areas, but its major pillars included historical understanding, economic cooperation, and security cooperation. In terms of economic cooperation, the two nations agreed to expand consultation on multilateral fora such as the World Trade Organization, OECD, and APEC. They also agreed on various security issues including North Korea’s denuclearization and reducing the threats of weapons of mass destruction. Considering the timing, it was a very profound and forward-looking declaration that highlighted various areas of cooperation and diplomacy.
However, over 25 years have passed and the two nations now need a more comprehensive, advanced declaration that can foster their relationship. A new joint statement is very timely and necessary, considering the changes in geopolitical and domestic political motivations. The return of U.S. President Donald Trump and his “America First” approach, coupled with reciprocal tariffs on both South Korea and Japan, has eroded U.S. credibility. It also accelerated the shift from a liberal trade world order toward mercantilist protectionism – pressuring both Seoul and Tokyo to diversify their economic partnerships. At the same time, China’s rapid technological ascent in sectors such as electric vehicles (EVs), display, batteries, and AI is reshaping both countries’ industrial strategies, demanding closer cooperation among like-minded economies.
Domestically, Lee’s political opponents accuse him of being anti-Japan and overly conciliatory toward Beijing. In order to combat these critics, Lee has to initiate a bolder, Japanese-friendly foreign policy, ultimately overcoming the mistrust conservatives have of his diplomatic strategy.
Simultaneously, Japan’s Prime Minister Ishiba Shigeru is grappling with declining approval ratings as shown by the consecutive Japanese elections, in which the Liberal Democratic Party and its coalition lost its majority in both houses of the Diet. Disputes over the terms of the U.S. trade deal and mounting economic pressure have left his political recovery uncertain, making foreign policy wins necessary for public support.
In this context, a successful bilateral engagement can not only recalibrate both nations’ relations but also set the stage for a more resilient regional order capable of alleviating protectionist shocks and ongoing technological competition in the Indo-Pacific.
The 2025 Lee-Ishiba joint statement did highlight certain areas of cooperation for a future-oriented bilateral relationship. Both nations agreed on the importance of advancing Japan-South Korea relations, following the theme of the Kim-Obuchi Joint Declaration. However, more needs to be done if Japan and South Korea are to exceed the level of cooperation reached in the 1990s.
Economic and Technological Cooperation
The joint statement included a heavy focus on cooperation in trade policies and emerging technology. Lee and Ishiba highlighted the importance of Japan-South Korea relations to tackle change in the international trade order. They agreed to enhance communication at all levels, including discussions on economic security, and utilize their complementary industrial strengths.
While Japan-South Korea-U.S. trilateral cooperation on supply chain management and economic security has strengthened in the past few years, state-level bilateral engagement and institutionalization has been lacking. This agreement fosters active communication through the formation of working groups and dialogues that can increase policy coordination when dealing with economic security threats. An institutionalized bilateral partnership focused on economic security will serve as a buffer against tariffs and trade wars, and foster resilience for both nations.
Furthermore, although the statement was vague on how, exactly, to utilize Japan’s and South Korea’s complementary industrial strengths, the direction of industrial cooperation is on the right track. This is already exemplary in supply chain management and sector-specific cooperation, especially in the semiconductor industry. Japan’s competitive position in advanced high-precision equipment, intermediate goods, and materials – such as semiconductor manufacturing machinery and specialty chemicals – for South Korea’s downstream industries like petrochemical and electronics can provide an opening for cooperation in supply chain management. Conversely, South Korea possesses innovative applications and scale advantages in those industries that can maximize the value of Japanese inputs. This will likely lead to a greater synergy for emerging technologies such as artificial intelligence (AI), clean energy, and other strategic technologies that were mentioned in the joint statement.
However, something was missing from the joint statement: prospects for building or strengthening multilateral trade regimes. Considering the global transformation from a liberal to a protectionist trade order, Lee should have actively looked for new opportunities by finding an agreement with Japan on joining the Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP). Parties to the CPTPP, of which Japan is a leading member, agreed to remove tariffs on more than 90 percent of trade items, meaning South Korea’s participation could mitigate the negative impacts from tariffs imposed by the United States.
Several nations as well as the European Union have shown interest in joining the CPTPP; thus far South Korea is not one of them. Although there have been news reports that the South Korean government has considered joining the CPTPP, previous administrations failed to make progress. Since both Japan and South Korea are also part of other multilateral forums such as the Indo-Pacific Economic Framework (IPEF) and Regional Comprehensive Economic Partnership (RCEP), collaborating in another forum will amplify their collective voice, help shape trade norms, and coordinate export control, labor, and environmental standards.
Stronger Trilateralism, But Dissonance in Regional Security
Another major pillar of cooperation that was mentioned in the Lee-Ishiba joint statement was cooperation in regional security. Both leaders agreed to commit to the complete denuclearization of the Korean Peninsula and multilateral cooperation to respond to North Korea’s missile and nuclear threats. At the same time, they highlighted the importance of the unwavering Japan-South Korea-U.S. trilateral cooperation, proving Lee’s stance to uphold pragmatism in foreign policy. This move could be interpreted as Lee’s signal to Washington, aimed at dispelling conservative concerns that he is conciliatory to China, while simultaneously underscoring South Korea’s willingness to demonstrate its value as a U.S. ally by advancing trilateralism.
Another notable piece of the summit was the bilateral discussion about regional security as a whole. During the press conference, Ishiba stated that, “both nations expressed opposition to any unilateral attempts to change the status quo by force or external pressure,” showing that their discussions expanded to the stability of the broader Indo-Pacific region. Before, South Korea limited its discussions with Japan mostly to peninsular issues, especially on how to either engage or pressure North Korea. Broader discussions with Japan about strengthening cooperation in the global and regional order should be seen as a stepping stone for the Lee administration to rethink South Korea’s contribution as a regional leader.
However, both nations failed to discuss the specifics of the regional order, especially on the issues that the United States is more concerned about. One of the pressing issues that South Korea needs to discuss with Japan is the potential for a Taiwan Strait crisis, and what role the two U.S. allies should play in such a contingency.
The Trump administration has been actively pressuring U.S. allies to prove how valuable they are to the U.S. grand strategy. For instance, Elbridge Colby, the U.S. undersecretary of defense for policy, has privately pushed Japan and Australia to commit to supporting the U.S. during a possible Taiwan contingency. Although the current Lee administration has not shown a clear message or strategy on the Taiwan issue, there is a possibility that, during Lee’s visit to Washington, the U.S. might press Seoul over South Korea’s role in a contingency, including questions about the strategic flexibility of U.S. Forces Korea activities outside of the Korean Peninsula.
Given Washington’s pressure on both Seoul and Tokyo, coupled with the potential economic disruptions that a Taiwan contingency could unleash, the Taiwan question has become a shared strategic challenge. This makes it imperative for the two U.S. allies to coordinate their positions. They could have used this summit not only to align their diplomatic stance but also to establish high-level channels for joint strategy planning and military responsibilities. But there was no indication such a discussion took place.
Another potential area of discussion could have been cooperation under AUKUS Pillar II – the Australia-United Kingdom-United States initiative focused on advanced capabilities like artificial intelligence, cyber, hypersonic, quantum, and electronic warfare. Lee has clearly shown his ambition to foster South Korea’s defense industry as a major economic driver, while Japan has signaled interest in joining these projects, providing a channel for both nations to synchronize strategic R&D of cutting-edge technologies.
Through this visit, both leaders should have jointly requested participation in AUKUS Pillar II, or at least started discussing ways to minimize the impact from the change of the U.S. foreign policy. This could have accelerated strategic interoperability, while also offering a credible justification for increased defense budgets, which the U.S. has pressed both nations to do. Defense investments made under AUKUS Pillar II can simultaneously function as contributions to burden-sharing and steps to bolster domestic industrial capabilities.
Next Steps
Ultimately, this renewed engagement will enable Seoul and Tokyo to become strategic partners, fostering an ecosystem of trust and interdependence that will reinforce the broader architecture of security and economic prosperity in the region. Yet, such progress cannot be taken for granted. It remains contingent on Japan’s willingness to confront its history with sincerity. This was something Lee underscored ahead of his trip to Japan. In his August 14 speech on the comfort women issue, he insisted that he “would spare no efforts to restore the victims’ honor and dignity.”
Nonetheless, there is reason for cautious optimism on Japan-South Korea rapprochement. Lee’s Independence Day address invoked the need for a shared future with Japan, while Ishiba’s remarks on the anniversary of Japan’s surrender shared his expression of remorse over World War II and acts of aggression – the first time a Japanese prime minister has used that word in over a decade. After his meeting with Ishiba, Lee suggested that “difficult issues” could be discussed “while cooperating in areas where collaboration is possible.”
If these sentiments translate into a concrete action even after this Japan-South Korea summit, the bilateral relationship may yet exceed the spirit of 1998 Kim-Obuchi Joint Declaration.