InterRegional for Strategic Analysis

Since early 2026, Japan–South Korea relations have undergone notable political, economic, and security developments. This marks a significant turning point for the two countries, following decades in which bilateral ties were dominated by historical disputes and grievances stemming from Japan’s colonial rule of the Korean Peninsula.Although these longstanding disputes remain unresolved, changes in the regional and international environment, coupled with growing security and economic challenges, have prompted Tokyo and Seoul to adopt a more pragmatic approach toward each other.Evidence of this shift has become increasingly apparent, particularly through the six bilateral meetings held so far in 2026. At the same time, this rapprochement raises important questions about its nature, the factors driving it, and the challenges that could derail it or prevent it from evolving into a deeper partnership in the near future.Key IndicatorsSeveral developments point to a growing rapprochement between Japan and South Korea in recent months, including the following:1. Agreement to Strengthen Bilateral LNG Cooperation: Following their meeting in May 2026, South Korean President Lee Jae-myung and Japanese Prime Minister Sanae Takaichi announced an agreement to expand bilateral cooperation in the energy sector, including <a href="https://www.spglobal.com/energy/en/news-research/latest-news/crude-oil/051926-south-korea-and-japan-to-strengthen-crude-lng-supply-security-cooperation" rel="noopener noreferrer" target="_blank">liquefied natural gas</a> (LNG). The agreement builds on a March 2026 arrangement between Korea Gas Corporation and Japan’s JERA concerning LNG swaps, while also expanding information-sharing and communication channels related to crude oil supplies and strategic reserves.2. Preliminary Agreement on Crude Oil Swaps: One of the most significant outcomes of the current Japan–South Korea cooperation has been progress in <a href="https://www.spglobal.com/energy/en/news-research/latest-news/crude-oil/051926-south-korea-and-japan-to-strengthen-crude-lng-supply-security-cooperation" rel="noopener noreferrer" target="_blank">supply-chain coordination</a>, particularly regarding critical minerals. The two sides agreed to launch a framework aimed at bolstering energy security through greater flexibility in crude oil, petroleum products, and LNG supplies, including resource-swap arrangements.In this context, South Korea’s Ministry of Trade, Industry and Energy and Japan’s Ministry of Economy, Trade and Industry agreed to encourage public-private dialogue on crude oil and petroleum-product swaps and reciprocal supply mechanisms. The arrangement is expected to allow each country to lend part of its strategic crude oil reserves to the other during emergencies, with the equivalent quantities to be returned at a later date.3. Launch of a Regular Government Dialogue to Address South Korea’s Restrictions on Japanese Food Imports: Japan is <a href="https://japantoday.com/category/national/japan-sounds-out-s.-korea-on-talks-to-lift-fukushima-seafood-curbs" rel="noopener noreferrer" target="_blank">seeking</a> to establish regular working-level consultations between its Ministry of Agriculture, Forestry and Fisheries and South Korea’s Ministry of Food and Drug Safety. The objective is to transform the issue from a politically sensitive dispute into an administrative and technical matter that can be managed through continuous institutional engagement.Such a mechanism could help reduce tensions surrounding South Korea’s restrictions on Japanese food imports—which were introduced following the Fukushima nuclear disaster—while simultaneously supporting broader trade cooperation between the two countries.On June 18, 2026, Japan’s Ministry of Agriculture organized an event in Seoul to <a href="https://www.nippon.com/en/news/yjj2026061800777/" rel="noopener noreferrer" target="_blank">highlight</a> the safety standards applied to Japanese food products as part of efforts to build momentum toward lifting South Korea’s ban on Japanese seafood imports.4. Calls for a Joint Economic Bloc to Strengthen Resilience: During the South Korea–Japan special session held as part of the 31st Future of Asia Forum in Tokyo on June 9, 2026, SK Group Chairman Chey Tae-won called for deeper economic integration between the two countries. He argued that bilateral relations should move beyond traditional industrial and commercial cooperation toward the creation of a broader and more comprehensive economic community.According to Chey, a joint economic bloc could create a <a href="https://www.upi.com/Top_News/World-News/2026/06/09/sk-group-chairman-remarks-japan-skorea-pursue-deeper-economic-community/5981781047907/#google_vignette" rel="noopener noreferrer" target="_blank">unified market</a> worth approximately $6 trillion, strengthening both countries’ ability to address growing economic and geopolitical challenges, while enhancing their competitiveness amid ongoing shifts in the global economy.5. Upgrading the Bilateral Security Dialogue: Japan and South Korea formally elevated their <a href="https://www.koreaherald.com/article/10733035" rel="noopener noreferrer" target="_blank">bilateral security dialogue</a> from the director-general level to a vice-ministerial "2+2" framework involving officials from both foreign and defense ministries.This upgrade was confirmed during the first vice-minister-level security talks held in Seoul on May 7, 2026. The move represents an important milestone in efforts to repair and deepen bilateral relations and signals a genuine willingness on both sides to address longstanding issues and strengthen cooperation.6. Resumption of Joint Military Exercises: Although military cooperation has not experienced major breakthroughs at the bilateral level, recent months have witnessed a noteworthy development. On June 7, 2026, Japan’s Maritime Self-Defense Force (JMSDF) and the Republic of Korea Navy (ROKN) conducted a joint <a href="https://thediplomat.com/2026/06/beyond-search-and-rescue-what-the-japan-south-korea-sarex-revival-really-means/" rel="noopener noreferrer" target="_blank">search-and-rescue</a> exercise (SAREX) west of Japan’s Goto Islands.The exercise marked the first bilateral naval drill of its kind in nine years. In addition to search-and-rescue operations, it included tactical data exchange exercises between ships and aircraft (LINKEX), cross-deck helicopter operations, and a joint maritime photography exercise (PHOTOEX).The Japanese Navy stated that the exercise enhanced search-and-rescue capabilities and strengthened bilateral cooperation. Its resumption following the December 2018 dispute—in which Japan accused a South Korean destroyer of directing fire-control radar at a Japanese P-1 maritime patrol aircraft—serves as a notable indicator of the improvement in bilateral relations between the two countries.Drivers of RapprochementSeveral factors have contributed to the growing cooperation between South Korea and Japan in recent months. The most notable drivers include the following:1. A Shared Interest in Addressing the Economic Impact of the Iran War: The conflict in the Middle East has posed a serious challenge for many Asian economies that depend heavily on energy supplies from the region. In particular, Japan and South Korea have been among the countries most affected by the conflict. According to data from the Korea National Oil Corporation (KNOC) and Japan’s Ministry of Economy, Trade and Industry (METI), Japan and South Korea rank as the world’s <a href="https://www.spglobal.com/energy/en/news-research/latest-news/crude-oil/051926-south-korea-and-japan-to-strengthen-crude-lng-supply-security-cooperation" rel="noopener noreferrer" target="_blank">fourth- and fifth</a>-largest importers of crude oil, respectively.Japan imports approximately 94% of its crude oil from the Middle East, while similarly, around 69% of South Korea’s crude oil imports originate from the Gulf region. This high level of dependence has prompted <a href="https://www.nytimes.com/2026/05/18/world/asia/lee-takaichi-meeting-korea-japan.html" rel="noopener noreferrer" target="_blank">both governments</a> to take additional steps to strengthen strategic cooperation across the political, economic, and security domains.2. The Growing Influence of Pragmatism in Foreign Policy Management: Despite <a href="https://www.nbcnews.com/world/asia/south-korea-japan-lee-jae-myung-sanae-takaichi-rcna345836" rel="noopener noreferrer" target="_blank">ideological differences</a> between South Korean President Lee Jae-myung and Japanese Prime Minister Sanae Takaichi regarding foreign policy issues, the pragmatic approach adopted by the South Korean president has contributed significantly to strengthening bilateral ties.Lee’s foreign policy approach is centered on maintaining South Korea’s alliance with the United States while simultaneously improving relations with China and North Korea, without allowing historical disputes with Japan to obstruct practical cooperation.Similarly, Prime Minister Takaichi has combined the firm security-oriented outlook associated with former Prime Minister Shinzo Abe with a pragmatic strategy aimed at safeguarding Japan’s economic and regional interests through cooperation with neighboring countries, including South Korea.3. Building on U.S. Support for Japan–South Korea Rapprochement: Successive U.S. administrations have demonstrated a strong commitment to fostering closer cooperation among America’s Asian allies, particularly Japan and South Korea. The historic <a href="https://www.csis.org/analysis/camp-david-us-japan-korea-trilateral-summit-exchange-among-csis-japan-and-korea-chairs" rel="noopener noreferrer" target="_blank">Camp David</a> Summit held on August 18, 2023, which brought together the leaders of the United States, Japan, and South Korea, remains the clearest example of this approach.The summit produced a joint statement committing the three countries to regular annual leaders’ meetings and deeper cooperation across multiple areas. This momentum has continued under the Trump administration, as U.S. trade policies have encouraged greater Japan–South Korea cooperation as a pragmatic response to shared economic challenges.At the same time, Washington has continued to encourage both Seoul and Tokyo to expand their defense cooperation.4. Washington’s Role in Promoting Defense Cooperation: Statements made by South Korean Defense Minister Ahn Gyu-back and his Japanese counterpart Shinjiro Koizumi during their meeting on the sidelines of the <a href="https://www.nknews.org/2026/05/south-korea-japan-stress-korean-peninsula-security-resume-maritime-drills/" rel="noopener noreferrer" target="_blank">Shangri-La Dialogue</a>, held from May 29–31, 2026, reflected a growing recognition that continued U.S. security guarantees in Asia require allies to assume greater defense responsibilities, move beyond historical grievances, and strengthen defense cooperation.Both ministers emphasized that bilateral cooperation, as well as trilateral cooperation with the United States, remains essential for preserving peace and stability on the Korean Peninsula and across the broader Indo-Pacific region.The current U.S. administration has also continued to encourage greater military coordination and integration between Japan and South Korea. For example, a series of trilateral activities involving the United States, South Korea, and Japan took place throughout 2025 to strengthen security cooperation.These efforts began with the <a href="https://atlasinstitute.org/american-japanese-korean-strategic-trilateral-pact-alliances-in-alignment/" rel="noopener noreferrer" target="_blank">Tri-CHOD</a> meeting in Seoul on July 10–11, where senior military leaders discussed ways to improve coordination and interoperability among their armed forces. This was followed by the multinational Freedom Edge exercise conducted in international waters near Jeju Island from September 15–19. The series concluded with a meeting of the three countries’ foreign ministers on the sidelines of the United Nations General Assembly in New York on September 22, 2025.During that meeting, the ministers reaffirmed their commitment to stability in the Indo-Pacific region and expressed concern regarding North Korea’s nuclear and missile programs, as well as China’s activities in the Taiwan Strait and the East China Sea. The United States also reiterated its unwavering commitment to the defense of both Japan and South Korea.5. Hedging Against the Possibility of U.S.–China Rapprochement: The recent U.S.–China summit, which was held in Beijing from May 13–15, 2026, reinforced Japanese concerns that the U.S. might <a href="https://thediplomat.com/2026/05/the-geopolitical-circumstances-of-japan-south-korea-rapprochement/" rel="noopener noreferrer" target="_blank">soften</a> its stance towards China and moderate its traditionally hardline policies, given that a pragmatic approach &nbsp;tends to prevail in the current administration.Deteriorating Sino-Japanese relations have amplified Tokyo’s concerns about a possible weakening of the U.S. security umbrella. As a result, Japan’s political leadership has increasingly pursued a proactive foreign policy aimed at minimizing secondary disputes with neighboring countries and supporting the security structures of nearby states.6. Deepening Cooperation Among China, North Korea, and Russia: China, North Korea, and Russia collectively represent some of the most significant security challenges facing both South Korea and Japan.North Korea’s advancing nuclear and missile capabilities remain the most frequently cited justification for closer security cooperation between Seoul and Tokyo. Meanwhile, China’s expanding naval presence in the East China Sea, the South China Sea, and the waters surrounding Taiwan constitutes a direct strategic challenge to both countries.In addition, the deepening political, economic, and security cooperation among <a href="https://edition.cnn.com/2025/07/16/asia/japan-defense-white-paper-china-russia-north-korea-intl-hnk-ml" rel="noopener noreferrer" target="_blank">China, Russia, and North Korea</a> has provided an additional incentive for Japan and South Korea to deepen coordination in response to shared regional challenges.Persistent ChallengesDespite the notable progress in bilateral relations, cooperation is unlikely to expand significantly beyond its current scope, particularly in the military domain. President Lee has previously indicated that he does not foresee a substantial expansion of military cooperation with Japan in the near term, arguing that historical disputes must first be addressed. He has also suggested that Japan should apologize for its past "hostile behavior" toward South Korea.Public opinion represents another major obstacle to closer ties, particularly in South Korea. President Lee remains mindful that rapprochement might carry electoral costs, especially given the continued sensitivity of historical and social issues in bilateral relations. These include disputes over Japan’s treatment of Korean women and laborers during the colonial period, as well as South Korea’s demands for <a href="https://thediplomat.com/2026/05/the-geopolitical-circumstances-of-japan-south-korea-rapprochement/" rel="noopener noreferrer" target="_blank">compensation</a> for affected individuals.Another potential source of tension lies in the two countries’ differing threat perceptions regarding China and North Korea. Japan generally adopts a more <a href="https://responsiblestatecraft.org/sanae-takaichi-japan/" rel="noopener noreferrer" target="_blank">assertive stance</a> toward China, whereas South Korea avoids publicly criticizing Beijing and seeks to balance its alliance with the United States with the need to maintain stable <a href="https://thediplomat.com/2026/01/south-koreas-delicate-balancing-act-amid-china-japan-discord/" rel="noopener noreferrer" target="_blank">relations</a> with China, given the importance of their economic and trade ties.With regard to North Korea, Japan has, at times, shown greater openness to engaging in dialogue with Pyongyang than South Korea.Nevertheless, a major breakthrough in Japan–South Korea relations over the coming years cannot be ruled out. In particular, the two countries may find themselves pushed closer together if regional and international developments create incentives for them to move beyond the longstanding disputes that have shaped their relationship for decades.

What’s Driving Rapprochement between Japan and South Korea