South Korean President Lee Jae Myung and Japanese Prime Minister Sanae Takaichi held their fourth meeting in about six months on Tuesday (May 19, 2026), underscoring their push to deepen ties between the historical Asian rivals in the face of geopolitical challenges.

Mr. Lee hosted Takaichi in his hometown of Andong, a southeastern South Korean city famous for a centuries-old traditional folk village that is a UNESCO World Heritage site. In January, the two met in Ms. Takaichi’s hometown of Nara, an ancient Japanese capital. The meetings marked the first time sitting leaders of the two countries have visited each other’s hometowns.

South Korea’s Presidential office expressed hope that Tuesday’s (May 19, 2026) summit would strengthen mutual trust between Mr. Lee and Ms. Takaichi. Ms. Takaichi told reporters earlier on Tuesday (May 19, 2026) that she hopes the talks will deepen cooperation “under the severe geopolitical conditions such as situations in the West Asia and the Indo-Pacific.”

The summit’s official agenda includes economic and energy cooperation, the Iran war and development of their bilateral ties, which have no current sticking points. Experts say the meeting likely will proceed smoothly and the relationship will remain on a positive trajectory for now.

“The two countries put more emphasis on agenda for cooperation than contentious issues,” said Choi Eunmi, a Japan expert at the Seoul-based Asan Institute for Policy Studies. “They would now think scenes of constantly fluctuating relationship or eventually negative bilateral ties won’t be helpful to anyone now.”

South Korea and Japan are both key U.S. allies with vibrant democracies. But their relationship has long experienced severe ups and downs over grievances stemming from Japan’s 35-year colonization of the Korean Peninsula before the end of World War II.

Relations began improving in 2023 when Mr. Lee and Ms. Takaichi’s predecessors took steps to move beyond history disputes and strengthen cooperation, saying they faced common challenges like the U.S.-China strategic competition, supply chain vulnerabilities and North Korea’s advancing nuclear arsenal.

When Mr. Lee and Ms. Takaichi each took office as new leaders last year, observers worried about Ms. Takaichi’s reputation as a right-wing security hawk and anticipation that Mr. Lee, a political liberal, would tilt toward North Korea and China and away from the U.S. and Japan. But they have maintained cooperation, even in some unprecedented ways.

In August, two months before Ms. Takaichi’s inauguration, Mr. Lee became the first South Korean leader to choose Japan as his first destination for a bilateral summit. At the end of their meeting in January, Mr. Lee and Ms. Takaichi drummed to K-pop hits such as BTS’ “Dynamite” in a jam session arranged by the Japanese leader, a heavy metal fan who was a drummer in her college days.

Mr. Lee has said he and Ms. Takaichi share a view that national leaders must act differently than ordinary politicians. But many observers say the two leaders also likely feel the need to tighten cooperation because they have more grave geopolitical difficulties than their predecessors such as U.S. President Donald Trump’s America-first policy and global economic damage caused by the Iran war.

South Korea and Japan both have pledged hundreds of billions of dollars in U.S. business investments. Mr. Trump’s tariff war and his transactional approach to security threaten the trust in the U.S. held by many South Korean and Japanese.

Ties between Seoul and Tokyo are so delicate they could suffer unexpected setbacks if they fail to formulate coping measures for explosive issues such as Japan’s colonial-era mobilisation of Koreans as forced laborers and sex slaves, according to experts, who say wrangling over those issues has eased as the two governments try to avoid public discussions.

“Both countries aren’t talking about how to resolve and prevent recurrences of conflicts over those issues and we don’t know when they could occur again,” Mr. Choi said.

Japan and the ‌United States are working to include a nuclear power project ​in the second round of deals under Japan’s $550-billion investment package, two ⁠people with knowledge of the matter told Reuters on Wednesday (March 4, 2026).

The nuclear power project, which the sources say will involve Westinghouse, is designed to strengthen both countries’ energy supply chains ‌as war in West Asia renews concerns about energy security.

Several deals have been under discussion, to be potentially announced when ‌Japanese Prime Minister Sanae Takaichi meets U.S. President Donald Trump in ‌Washington ⁠on March 19, said the sources, who declined to be ⁠identified as the matter was private.

Tokyo is scrambling to build up deals under the investment commitments it made as part of a U.S. tariff agreement. It has already announced three projects ​valued at $36 billion, including a natural ‌gas power plant in Ohio.

A project to construct a copper smelting and refining facility is also being considered, the sources said. Aiming to deepen the talks, Japan’s Trade Minister Ryosei Akazawa plans to visit the ‌U.S. from Thursday (March 5, 2026) to meet U.S. Commerce Secretary Howard Lutnick, two ​separate sources close to the matter said on Wednesday (March 4, 2026).

Westinghouse was one of about 20 companies mentioned in a joint fact sheet ⁠the two governments issued in October as having expressed interest in projects to be financed by Tokyo.

The U.S. company, owned by Cameco and Brookfield , ‌is looking at building pressurised water reactors and small modular reactors totalling up to $100 billion, according to the fact sheet.

Japanese firms such as Mitsubishi Heavy Industries, Toshiba and IHI could be potentially involved, it said. Last year, the U.S. government inked a partnership worth at least $80 billion with Westinghouse to build nuclear reactors, underlining Mr. Trump’s agenda to increase domestic energy output as the ‌expansion of artificial intelligence data centres boosts demand.

The fact sheet also said Falcon Copper ​was considering building a $2 billion copper smelting and refining facility and is exploring involvement from Japanese suppliers and off-takers.

An official at ⁠Japan’s industry ministry said the government did not know how the negotiations would ⁠turn out. Mitsubishi Heavy said nothing had been decided and that it would assess any equipment supply on a case-by-case basis. Toshiba ‌declined to comment.

IHI said it would review details if concrete talks emerged. Westinghouse and Falcon Copper could not be reached for comment outside their ​business hours.

Japanese Prime Minister Sanae Takaichi sparked a controversy when she said that a Chinese assault on Taiwan could be deemed a “survival-threatening situation” — a legal justification allowing Tokyo to exercise collective self-defence. China claims sovereignty over Taiwan, a position Taipei firmly rejects.

Ms. Takaichi’s refusal to retract the statement caused bilateral ties to unravel at an alarming speed. The dispute has become the region’s biggest crisis in recent years, characterised by Chinese military sorties, economic coercion against seafood imports, and a blanket freeze on cultural exchange. Having failed to force a retraction, Beijing has escalated the issue to the United Nations, framing Japan’s stance as a threat to the post-war international order.

Japan’s post-war Constitution forbids it from using force as a means of settling international disputes but a 2015 law, passed when Ms. Takaichi’s mentor, Shinzo Abe, was Prime Minister, permits it to exercise collective self-defence in certain situations, even if it is not directly under attack.

The kerfuffle over Ms. Takaichi’s remarks comes just as Japan faces significant domestic headwinds. The world’s fourth-largest economy is facing slow economic growth and persistent inflation.

The Prime Minister is attempting to solve these issues with new stimulus measures. Further compounding these challenges is a long-term fertility crisis, with the country’s population growth turning negative since 2011.

Against this backdrop, a prolonged rift with China could be problematic, given that Beijing is Japan’s largest trading partner. China accounted for 20% of Japan’s imports and exports each, between 2018 and 2024.

Bloomberg notes that Japanese manufacturers rely heavily on Chinese critical materials. Reuters reports that China provides 60% of Japan’s rare earths — key components for cars and electronics.

The power of this monopoly was demonstrated recently when China used its rare earth dominance to successfully pressure the U.S. into lowering tariffs. China has told tourists not to visit Japan, stopped approvals of new Japanese firms, and restricted Japanese seafood.

Ms. Takaichi’s suggestion that Japan might intervene in a Taiwan Strait conflict underscores the importance of this maritime route to Tokyo. The chart below illustrates the total trade volume by country passing through the Strait in 2022 (excluding China). Japan stands out significantly, with over $440 billion in trade relying on this waterway.

Much of the trade between the two neighbours would be disrupted if tensions in the Strait rise. Taiwan is a vital trading partner for Japan, particularly for critical technology. In 2025 (till September), Japan sourced 60% of its integrated circuits and over 50% of its semiconductors from Taiwan, along with significant volumes of electrical machinery.

Tensions are also mounting over the military implications of Ms. Takaichi’s remarks. In 2025, Japan’s defence spending hit a 70-year high of 1.8% of GDP, a level not seen since the 1950s.

On Wednesday, Taiwanese President Lai Ching-te said that his government is going to propose $40 billion in additional defence spending in the coming years.

In 2024, Japan’s forces ‘scrambled’ over 700 times in response to Chinese and Russian aircraft violations. A ‘scramble’ refers to the emergency dispatch of aircraft by the country’s Air Self-Defence Force when an unidentified aircraft is suspected of violating Japanese airspace.

The data for the charts were sourced from the World Bank, the Centre for Strategic and International Studies (CSIS), UNCOMTRADE, SIPRI, Defence of Japan 2025, and e-Stat: a portal site for Japanese Government Statistics.