By Eric Vandenbroeck and co-workers

When the leaders of China, Japan, and South Korea last met, in May 2024, observers viewed the meeting with a sense of relief. Japan and South Korea were emerging from one of the darkest periods in their bilateral relationship, when tensions over Japan’s colonial legacy in Korea had become so intense that they derailed traditional areas of cooperation in security and trade. In 2018, leaders in Tokyo reported that a South Korean warship had locked its radar on a Japanese patrol plane, and in 2019, the two countries launched a tit-for-tat escalation, in which Tokyo tightened export controls, and Seoul responded by threatening to stop sharing intelligence. The substantive but fragile rapprochement between the two U.S. allies starting in 2022 allowed them to engage a powerful and assertive Beijing in a two-against-one dynamic.

Strengthening the Japanese–South Korean partnership is increasingly important as China flexes its muscle in the region. In November, Beijing launched a pressure campaign against Japan in response to remarks by Sanae Takaichi, the newly inaugurated prime minister, suggesting that Tokyo could get involved militarily if China were to attack or blockade Taiwan. China suspended seafood imports from Japan, canceled Japanese concerts and movie releases, and advised citizens against traveling to Japan. The Japanese Defense Ministry also reported that Chinese fighter aircraft had locked their radar on Japanese planes. It’s a familiar playbook for Beijing, which took many similar actions against South Korea when Seoul agreed to host a U.S. missile defense system, known as THAAD, in 2016–17. South Korea has so far stayed neutral in response to China’s pressure campaign against Japan, which reveals the lengths that Seoul and Tokyo still have to go before they can team up to counter Beijing’s coercion and deal with other pressing regional challenges, including newfound uncertainty about U.S. commitments and a strengthened axis of China, North Korea, and Russia.

The fate of Japanese–South Korean relations at a crucial moment may ultimately rest on the two countries’ new leaders, who, at first glance, do not seem to be natural partners. South Korean President Lee Jae-myung, who took over in June, has strong credentials on the South Korean left, which traditionally seeks engagement with Pyongyang—and, by extension, better relations with Beijing—and is less focused on strengthening the trilateral security partnership with Japan and the United States. South Korean progressives are also more inclined to call attention to Japan’s mistreatment of Koreans during its colonial rule and are willing to challenge existing bilateral arrangements for reparations. Meanwhile, Takaichi comes from the right wing of Japan’s dominant Liberal Democratic Party and represents the group most resistant to accommodating what it sees as South Korea’s continuous demands to address past injustices. She has visited the controversial Yasukuni Shrine, the memorial to Japanese soldiers that includes 14 convicted war criminals from World War II, and is a protégé of the former Prime Minister Shinzo Abe, whose revisionist views on history inspired deep antipathy among the South Korean public.

But this unlikely duo could be precisely the partnership needed to put the Japanese–South Korean relationship on a more resilient footing. The differing coalitions they represent will allow them to build a partnership with broader and more durable political support at home. Cooperation that takes root under this type of pairing is more challenging than that between two like-minded leaders, of course, but when it succeeds, it is more likely to endure. Takaichi and Lee are thus uniquely positioned to stage what might be called “Nixon goes to China” moments in their countries: because they are not expected to try rapprochement, these two recently elected leaders have the potential to break the cycle of disruption in the Japanese–South Korean partnership and to establish a lasting basis of cooperation.

 

Squeezed From Both Sides

Upon Takaichi’s inauguration in October, the South Korean left expressed apprehension about the right-wing policies they expected from her government. Likewise, when Lee won the election in June after President Yoon Suk-yeol’s impeachment, many Japanese observers questioned whether he would cooperate with Japan, given his earlier harsh denunciations of its historical actions and its release of treated wastewater from the Fukushima nuclear power plant into the Pacific Ocean in 2023. Although Lee moderated his tone and adopted a friendlier posture toward Japan when he assumed office—choosing Tokyo rather than Washington or Beijing as his first foreign destination—many in Japan doubted he would maintain his conciliatory stance when dealing with a conservative politician such as Takaichi.

The mistrust and frustration have deep roots. Both countries have struggled to strike a sustainable bargain over Japan’s colonial legacy in Korea, including whether and how Japan should offer apologies and compensation for its exploitation of “comfort women” and use of forced labor in wartime. South Korean court rulings challenging the 1965 bilateral settlement of historical claims have interrupted the two governments’ diplomatic efforts to advance their strategic partnership. After the South Korean Constitutional Court held the government accountable for not doing enough to seek compensation from Tokyo on behalf of comfort women in 2011, and with his administration facing declining domestic support, the conservative President Lee Myung-bak retreated from his attempts to improve ties with Japan and adopted a more confrontational position. His conservative successor, Park Geun-hye, signed a new compensation package with Abe to support comfort women survivors in 2015, explicitly stating that the issue was resolved “finally and irreversibly.” Yet when the progressive Moon Jae-in took office in 2017, he discredited the deal, shattering Japan’s trust in South Korea as a negotiating partner.

By the time the conservative Yoon became president in 2022 and sought rapprochement with Tokyo, Japanese officials were so fatigued that they initially hesitated to reciprocate. Japanese leaders had learned that deals struck with willing South Korean conservatives often reflected support from only half the electorate and could easily be undone when their political fortunes diminished or progressive successors took office. At the encouragement of the Biden administration, Yoon and then Prime Minister Fumio Kishida eventually restored shuttle diplomacy, intelligence sharing, and chip component exports, culminating in a historic Camp David joint statement in 2023 committing Japan, South Korea, and the United States to consult in the event of a regional contingency, implying that the countries would possibly coordinate to respond to a Chinese invasion of Taiwan. Yet many officials and analysts wondered whether these advances would survive another leadership transition or domestic political crisis in Seoul. For Japan, genuine reassurance could only come from someone least likely to offer it: a progressive South Korean leader.

South Korea, meanwhile, also needs a cooperative bargain with a conservative Japanese leader if any deal is to stick. In 1995, to mark the 50th anniversary of the end of World War II, Japanese Prime Minister Tomiichi Murayama, a socialist, issued a statement of apology for Japan’s wartime actions and colonial rule. The new generation of conservative politicians, including Abe and Takaichi, openly questioned the necessity of an apology and took issue with its content. Although both leaders ultimately upheld the Murayama statement as cabinet ministers, this backlash from Japan’s right fueled South Korean suspicions about the sincerity of Japan’s apology.

More recently, Kishida, who was prime minister from 2021 to 2024, and his successor, Shigeru Ishiba, who led Japan until he resigned in 2025, represented relatively liberal factions within the Liberal Democratic Party. But because of their liberal image, both faced pressure to appeal to more conservative forces. Kishida accommodated many conservative policy priorities, such as restarting nuclear power plants and expanding the military; Ishiba faced criticism from his right flank for being too conciliatory toward Beijing. When Ishiba met with Lee in August, conservative opinion leaders and Takaichi supporters doubted his willingness to take a firm stance to protect Japan’s national interests, limiting his ability to act decisively to offer concessions to South Korea.

 

Low Expectations, High Rewards

Takaichi, unlike her more liberal predecessors, can govern with both the authority and legitimacy to engage Seoul without fear of being undermined by the political right in Tokyo. She is unlikely to offer new apologies or drastic concessions on historical issues beyond what Abe did when he expressed Japan’s “deep repentance for the war” in a statement commemorating the war’s 70th anniversary and proposed a one-time offer to compensate South Korea in the 2015 comfort women agreement. But Takaichi can pursue sustained dialogue with counterparts in Seoul and push to elevate the Japanese–South Korean relationship into a bilateral strategic partnership with the full backing of Japan’s conservative establishment. With her coalition government securing a majority in the lower house of parliament in late November, Takaichi is positioned to gradually build a firmer domestic footing to carry out these efforts.

To govern effectively as a progressive amid increasingly polarized South Korean politics, meanwhile, Lee needs to secure centrist support. Improving the relationship with Japan is among his best options for implementing a pragmatic agenda. The foreign policy positions of his predecessor—especially rapprochement with Japan—were relatively popular among the South Korean public despite Yoon’s troubled presidency and eventual impeachment. The Lee administration has therefore appointed moderates to key diplomatic posts, such as national security adviser, and Lee can further empower them while pushing back against more hard-line forces by demonstrating the tangible benefits of cooperation with Tokyo.

Luckily, Takaichi and Lee do not need to build a relationship from scratch. They can capitalize on the momentum of their predecessors. Kishida and Yoon agreed in 2023 to collaborate in fields of intense geopolitical competition, including quantum computing, artificial intelligence, biotechnology, and supply chain resilience. And after Ishiba and Lee met in August, a joint committee on science and technology cooperation between their two countries convened in November—the first such high-level meeting on the subject in 16 years.

The deteriorating security environment in the Indo-Pacific makes it even more necessary for these leaders to collaborate. In particular, Washington’s renewed unpredictability and waning engagement in multilateral forums require Japan and South Korea to work together to sustain regional public goods and protect their interests. Yoon officially embraced Japan’s vision of a free and open Indo-Pacific, an Abe-era strategy for promoting a rules-based regional order that his successors have maintained and that Takaichi seeks to revitalize as the core of her foreign policy vision. Japan can promote South Korean leaders’ efforts to join various minilateral and multilateral platforms, including the Comprehensive and Progressive Agreement for Trans-Pacific Partnership, the free-trade pact that emerged from the Trans-Pacific Partnership, and, in the long term, the G-7. Japan should also embrace South Korea’s regular participation—even if only as an observer—in the security partnerships between Australia, India, Japan, and the United States, known as the Quad, or between Australia, Japan, the Philippines, and the United States, informally called the “Squad.” Adding South Korea to these coalitions will streamline overlapping partnership-building efforts and boost Tokyo’s and Seoul’s ability to pool resources and collectively build enough military, economic, and technological scale to compete with China and its allies.

Such outcomes are not guaranteed, however. The last time the two countries had a similar combination of leaders was from 2017 to 2020, when the conservative Abe led Japan, and the progressive Moon was president of South Korea. Moon entered office determined to reverse his predecessor’s successful efforts to improve ties with Tokyo, which soured relations from the outset and led to further tensions. There is also a risk that a diplomatic contingency, such as renewed disputes over a contested set of islands between the two countries known as Dokdo in South Korea and Takeshima in Japan, could rile up nationalist sentiment and halt political momentum for cooperation.

But there is reason to believe that the current leadership pairing could herald genuine progress. When world leaders met for sideline meetings at the Asia-Pacific Economic Cooperation forum in October, Takaichi and Lee surprised their domestic audiences with an overwhelmingly positive encounter. The Japanese prime minister, who had expressed fondness for South Korean cosmetics, seaweed, and television dramas days earlier, bowed to the South Korean flag—a move considered respectful that was widely covered in the South Korean press. After the summit, the South Korean president, for his part, told a domestic audience that he was “no longer worried” about having Takaichi as his counterpart, a statement embraced by Japanese media. Lee is reportedly considering traveling to Tokyo to visit Takaichi in January 2026. By deepening cooperation across ideological lines and managing expectations, Tokyo and Seoul have a rare opportunity to construct an alignment resilient enough to withstand the political winds of the future.

 

 

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