Key Takeaways

-       South Korea and Japan have made historic strides in bilateral relations under President Lee, with the first joint statement in 17 years and enhanced trilateral cooperation with the U.S.

-       To sustain momentum, both countries should institutionalize cooperation through security and economic “2+2” meetings, military exchanges, and joint initiatives addressing shared domestic and industrial challenges.

-       Expanding civil and private sector engagement—including youth programs, cultural exchanges, and corporate partnerships—can strengthen resilience and create a future-oriented, practical partnership beyond political fluctuations.

Japanese Prime Minister Shigeru Ishiba announced his resignation on September 8, putting a hold on recent momentum to strengthen the South Korea-Japan relationship after a symbolic summit with President Lee Jae-myung in August.

Earlier this year, the main concern in the bilateral relationship was whether Lee would emulate the conciliatory approach to Japan like his predecessor Yoon Suk-yeol, or a more standoffish approach similar to Moon Jae-in. Now, the concern lies in Tokyo, where the new prime minister could continue building on the last two successive prime ministers’ work or abandon the positive path toward a stronger South Korea-Japan partnership.

Changes in governments have historically halted and soured bilateral relations between the two countries. But instead of taking a more cautious approach, the uncertainty in international affairs requires the two countries to continue deepening cooperation.

To elevate bilateral relations to a new stage, South Korea and Japan should commit to a future-oriented relationship not just symbolically — like with talks of updating the 1998 joint declaration — but a practical agenda that outlines steps to achieve cooperation in areas of common interest.

​​Despite the initial concerns over President Lee’s perceived anti-Japan stance inferred from his past remarks, his first 100 days in office, when it comes to ROK-Japan relations, proved to be a relatively positive surprise.

First, two meetings between the two leaders have established the basic foundation for continued cooperation: one during the G7 Summit in June and an official bilateral summit in August. The August summit marked Lee’s first state visit since his inauguration and produced a joint statement — the first in 17 years between leaders of the two countries — encompassing cooperation across regional security, people-to-people exchange, future industries, and global partnerships. The timing of the summit, scheduled immediately before Lee’s state visit to the United States, along with the two leaders’ shared perceptions on critical regional and domestic issues, signaled how both capitals recognize each other’s strategic importance in their respective diplomatic frameworks.

Second, substantive meetings and dialogues beyond the symbolic summitry have followed to create meaningful developments and carry this momentum. The Defense Ministers’ Meeting on September 8 — marking the first visit by a Japanese defense minister to Seoul in a decade — reaffirmed commitments to denuclearize the Korean peninsula, deepen trilateral cooperation, and expand partnerships in emerging technologies and new frontiers including space, artificial intelligence, and autonomous weapons systems.

Trilateral cooperation with the United States appears to have maintained its momentum, at least for now, with both Seoul and Tokyo consistently emphasizing its strategic importance through high-level engagements, including meetings between foreign ministers, deputy and vice foreign ministers, Joint Chiefs of Staff (Tri-CHOD), as well as expanded and continued working-level cooperation on quantum industrial security and North Korea’s escalating cybersecurity threats.

Reframing bilateral relations as a “future-oriented partnership” will not be easy. Decades of mistrust and instances of high tension have left a visible mark on the bilateral relationship.

Yet, the list of shared challenges continues to grow, from China’s actions to assert itself in the Indo-Pacific region to uncertainty over U.S. commitment to the region to socioeconomic issues like depopulation. There are several streams of effort that the two countries can take to move from the past and carry the present momentum into the future.

First, a shift in mindsets on both sides must take place. For far too long, both South Korea and Japan have come to expect bilateral relations to come in fits and starts. A culture of continuity must be fostered in a way that moves beyond political narratives and mutual distrust every time a new leader enters the fray in either country. For instance, despite lingering concerns over the consistency of South Korea’s Japan policy, Lee has proven thus far that he practices what he preaches: practical diplomacy that requires stronger relations to be built with Japan.

Japan’s new leader — whether that be the moderate leaning Shinjiro Koizumi or conservative Sanae Takaichi or someone else — should also be given the benefit of the doubt to take time to assess the value of the bilateral relationship. Domestic political narratives quickly jump to the conclusion that seeking closer ties with the other country represents weakness or a lack of appreciation for past grievances. This narrative has to shift to one in which bilateral relations are viewed as a strategic asset in an uncertain world rather than a liability.

Second, the two countries should institutionalize areas of cooperation and set a realistic roadmap for how to practically deepen cooperation. A huge step that would indicate the fundamental redrawing of relations would be to set up a security consultative committee (2+2) and an economic “2+2” meeting between relevant ministers, which Japan conducts with important allies and partners. These forums can serve as a high-level dialogue to discuss anything from defense industry cooperation to supply chain resilience to sharing information on common regional challenges. This would elevate the ad hoc “2+2” between senior foreign and defense ministry officials last held in 2023.

The two countries can also explore avenues for military-to-military cooperation, something that has been kept off the table in defense talks given diverging strategic focus points (Korean Peninsula vs. East China Sea). While mutual defense minister visits and routine senior official dialogues are important, the two countries could pursue unit-level exchanges to understand the situations each country faces in their respective backyards and to promote trust building without immediately jumping into sensitive areas like joint contingency planning or signing a reciprocal access agreement.

Other areas of cooperation should be strengthened too, such as addressing shared domestic challenges like demographic decline and regional revitalization by doubling down on knowledge sharing and pursuing joint projects. The next step after creating institutions would be to secure constant communication and design research projects or create financial incentives for businesses to invest in rural areas in both countries.

Third, civil engagement between the two countries must not only continue but expand. The record-high numbers for tourist exchanges last year, driven particularly by a surge of Korean visitors to Japan, have certainly contributed to the warmer public perceptions of each other. A joint survey by Yomiuri Shimbun and Hankuk Ilbo in June revealed that the majority of both Korean and Japanese respondents believe their nations enjoy good bilateral relations, while approximately 40 percent expressed cultural favorability. The Hankuk Research’s July survey on neighboring countries also recorded the highest-ever favorability rating for Japan (42.7 percent) in the survey’s history. In both studies, citizens between 18 and 29 who have greater cultural exposure to one another and lesser historical memories reported the highest favorability among all age groups.

This cultural asset should be translated into policy actions and sustained dialogues. Beyond mere cultural exchanges, both governments and NGOs should promote policy and educational engagements between the youth of both countries in order to foster the mutual understanding of bilateral relationship’s importance and nurture a future-oriented mindset focused on cooperation rather than divisions. The area of exchanges should also cover broader common domestic challenges and industrial objectives, such as talent development in strategic industries such as artificial intelligence and quantum technology through joint educational and research-oriented initiatives. When such collaborative habits and conversations take place, more sensitive topics that have historically strained the bilateral relationships, including historical disputes, can be addressed more naturally and with less political burden.

Seoul and Tokyo must remember how swiftly and dramatically public perceptions deteriorated during the 2019 trade dispute stemming from disagreements over forced labor compensation. Civil engagements and the underlying rapport between societies form a foundation that will keep the two countries close even when tested by domestic and foreign pressures – preventing disagreements from escalating into lasting divisions. Hence, both leaders would be wise to capitalize on the current momentum to foster deeper and more resilient engagements.

Lastly, private sector engagement must be elevated as a cornerstone of the bilateral relations, with governments promoting and supporting dialogue and cooperation between corporations navigating similar external environments, such as U.S. pressures and the need for technological innovation in an increasingly competitive global landscape.

Both governments could strategically encourage wider collaborations between corporates through joint ventures and similar initiatives, especially given how Korean and Japanese companies face parallel challenges with the new U.S. investment packages and supply chain diversification requirements following America’s reshoring strategy. The partnerships between companies could certainly leverage complementary strengths while sharing risks in the third-country markets, mutually benefiting from their expertise and capital. The LG Energy Solutions-Toyota Tsusho joint venture in North Carolina exemplifies this approach, highlighting how strategic partnerships can simultaneously address external policy pressures for domestic production while maintaining competitiveness in critical sectors like electric vehicle batteries.

Simultaneously, this effort should be accompanied by expanded dialogue between business leaders via institutionalized regular conferences, high-level delegations led by organizations such as Keidanren and KCCI, and government-facilitated forums. Existing programs like the Korea-Japan Business Conference that have proved effective in promoting cooperation should be sustained and even expanded to include a broader range of companies from diverse industries and scales of operations. Such systematic engagement creates resilient economic foundations that can withstand political fluctuations and provide practical incentives for continued cooperation.

The 1998 joint declaration by President Kim Dae-jung and Prime Minister Keizo Obuchi dramatically developed Korea-Japan relations, providing a blueprint for comprehensive future-oriented partnerships rooted in historical reconciliation and shared international objectives. Two decades later, this landmark declaration remains the gold standard, with successive leaders — from former President Yoon Suk Yeol's ambitious upgrade initiatives to President Lee’s explicit reference to the 1998 framework — consistently returning to its foundational principles. But now is the time for the bold upgrade of these principles.

If Kim and Obuchi showcased the vision to revolutionize bilateral relations in 1998, today’s leaders face an even more compelling imperative to elevate this partnership for the challenges ahead. For this to happen, both nations must move beyond the counterproductive cycle of worrying about new leadership causing disruptions, but focus instead on a positive agenda addressing what must be accomplished given the rapidly shifting regional and global environment. The foundation laid a quarter-century ago now requires structural reinforcement to withstand the pressures and opportunities of our current era.