On May 15, the South Korean presidency confirmed that Japanese Prime Minister Takaichi Sanae will pay a two-day visit to South Korea starting May 19. The location of this high-level visit will be the city of AndongGyeongsangbuk province, hometown of South Korean President Lee Jae-myung. The meeting is considered a continuation of the Japan-South Korea Summit earlier this year when Lee visited Takaichi’s hometown, as well as an attempt to further institutionalize shuttle diplomacy between the two leaders. It will also serve as a new test for bilateral cooperation as both sides seek to strengthen coordination in security, economic affairs and regional stability.
The timing of the meeting between Seoul and Tokyo is particularly noteworthy, as it comes immediately after the China-US summit that concluded on May 15. Amid intensifying strategic competition among major powers and an increasingly volatile regional security environment, Japan and South Korea share growing strategic interests as well as common security concerns, particularly regarding the risk of disruptions to energy supply chains following the crisis in the Strait of Hormuz.
The recent China-US summit quickly became the center of international attention, as it marked US President Donald Trump’s second visit to China – while also representing the first time in nearly a decade that a sitting US president made an official visit to the country. Immediately after the conclusion of the Trump-Xi meeting, Japan and South Korea officially announced their intention to hold a bilateral summit to discuss regional issues as well as prospects for the development of Japan-South Korea relations. The move can be seen as a form of follow-up response, reflecting the two countries’ close observation of the two superpowers’ reactions and strategic calculations after the summit, while also illustrating the timely strategic adjustments made by Seoul and Tokyo in an increasingly uncertain environment.
For decades, relations between South Korea and Japan have fluctuated due to prolonged historical and political friction, despite the fact that the two countries continue to share many common values, strategic interests, and a similar geopolitical environment marked by comparable security threats. As two key U.S. allies in East Asia, Tokyo and Seoul have long competed with and depended on each other within the Washington-led regional security structure. However, changes in the US approach to its allies under Trump’s second term, combined with intensifying great power competition and growing economic and energy security risks, are providing further incentive for South Korea and Japan to draw closer together.
Trump is ambiguous Remarks during his meeting with Xi Jinping, notably those seen as referring to Taiwan, as well as his limited attention to the North Korea nuclear issue, have generated two common forms of security anxiety among U.S. allies in East Asia: fear of abandonment and fear of being trapped in U.S.-led conflicts. Within an asymmetric alliance structure, in which smaller states accept partial constraints on strategic autonomy in exchange for security guarantees from a major power, allies are often the most vulnerable targets when the patron state changes its strategic thinking or policy priorities.
Tokyo and Seoul are naturally well aware of this reality. Therefore, while maintain Despite their close relations with Washington, despite pressures related to tariffs, defense burden sharing and trade imbalances, Japan and South Korea are also gradually activating “self-help” mechanisms aimed at minimizing strategic risks. This does not mean that the two countries are attempting to dissociate themselves from the U.S. alliance framework, but rather reflects a broader effort to improve strategic adaptability by expanding bilateral cooperation, diversifying diplomatic networks, and building resilience.
Pressure from the international environment could make security one of the central pillars of the agenda of the third Lee-Takaichi summit. Tokyo and Seoul share concerns not only about tensions around the Taiwan Strait and the threat posed by North Korea’s nuclear program, but also about the possibility that an escalation of conflict could undermine economic security and disrupt supply chains.
When the Strait of Hormuz crisis erupted, Japan and South Korea were among the countries hardest hit by disruptions to energy supplies supporting strategic industries. Statistics show that Japan has been dependent on the Middle East for approximately 90 percent of its crude oil imports, while South Korea’s dependence stands at around 70 percent. The conflict between Iran and the United States has not only created instability in fuel supplies, but also has arrived oil prices, putting significant pressure on the economies of South Korea and Japan, both of which are among the the largest in the world importers and consumers of crude oil.
As a result, unlike many previous Japan-South Korea summits which mainly focused on dealing with historical heritage, this summit’s agenda is expected to focus more on discussion alternative solutions to the traditional energy lifeline passing through the Strait of Hormuz, as well as measures to ensure the safety of maritime shipping routes in the region. Before that, South Korea and Japan had already tried to diversify supply chains and explore safer and more viable shipping routes. This demonstrates that energy security is gradually becoming an integral part of Japan and South Korea’s strategic security thinking, rather than remaining simply an economic, commercial or historical issue as in the past.
Another issue that could emerge during the third meeting between Lee and Takaichi is the possibility of a bilateral acquisition and cross-services agreement (ACSA). May 7, 2026, during the first vice-ministerial level “2+2” As part of the dialogue between the foreign and defense ministries of South Korea and Japan, the two sides discussed the possibility of establishing a military logistics exchange and support mechanism.
However, representatives of South Korea’s Ministry of National Defense quickly stated during the discussions that Seoul currently has no plans to sign such an agreement with Tokyo. Concerns arise primarily from the possibility that an ACSA could open the door to a greater presence of Japanese Self-Defense Forces on the Korean Peninsula during emergencies, as well as fears that excessive military and security alignment with Japan could provoke backlash from North Korea and China.
Nonetheless, the ACSA issue could still become an important topic on the summit agenda, particularly at a time when strategic maritime routes in East Asia and the Middle East remain vulnerable to disruption. Furthermore, Trump’s limited attention to the North Korean nuclear issue during his meeting with Xi Jinping, as well as his ambiguous statements on Taiwan, are raising growing concerns in Tokyo and Seoul about the need for greater coordination and mutual support during possible regional crises.
In this sense, the ACSA is not simply a technical agreement on military logistics, but also reflects the level of strategic trust and operational coordination between Japan and South Korea. It is now considered one of the most sensitive issues in bilateral relations, as it could both trigger anti-Japanese sentiment in South Korea and potentially become a turning point that would move Tokyo-Seoul relations from symbolic cooperation to more substantive security coordination.
Beyond energy and traditional security concerns, critical mineral supply chains are also expected to become an important issue on the agenda between Tokyo and Seoul. In a context of increasingly fierce competition in high-tech sectors, mining security is becoming a crucial element of national development and economic security strategies. A report from the Observer Research Foundation showed that Japan and South Korea are both pursuing “reduce the risks» and diversification strategies in critical minerals supply chains to build resilience to external shocks while reducing over-reliance on China.
So far, Japan and South Korea have accelerated their investments in mining and resource security. Since 2018, the Japanese government has invested approximately $256 million in deep-sea mining development projects, while South Korean companies Countries are expanding their mining investments abroad in an effort to diversify their sources of raw materials. By cooperating, South Korea and Japan may be able to leverage their complementary strengths across the value chain to strengthen their resilience to supply-side pressures, while creating a new form of strategic leverage against China’s increasing politicization of critical minerals supply chains.
Relations between Japan and South Korea could enter their most stable and open phase in nearly a decade, thanks to the growing convergence of security, economic and strategic interests between the two leaders. The promotion of “local shuttle diplomacy” shows that under Lee Jae-myung and Takaichi, Tokyo and Seoul are not only seeking to manage short-term frictions, but are also trying to build a more sustainable basis for trust-based cooperation and long-term strategic coordination.
At a broader level, this trend also reflects the increasingly visible strategic adjustment of middle powers amid intensifying great power competition and a more unpredictable alliance environment. As major powers’ security commitments are no longer seen as absolute guarantees, countries like Japan and South Korea are increasingly seeking to strengthen their strategic resilience through bilateral cooperation, diversification of external relations, and expansion of more practical coordination mechanisms.
In this sense, the third Lee-Takaichi summit could not only indicate a step forward in South Korea-Japan relations, but also reflect a change in the strategic perception of US allies in East Asia in response to an unstable and unpredictable regional environment.