During his visit to Japan in January, Korean President Lee Jae Myung demonstrated clear rapport with Japanese Prime Minister Sanae Takaichi, culminating in the two leaders performing a live drum duet.
The video footage and images that emerged from the duet were a remarkable piece of political communications in a modern media environment too often characterized by divisive rhetoric and polarization. But beyond the K-pop beat, a deep and durable bilateral relationship between South Korea and Japan is beginning to emerge based on a shared assessment of the region’s primary security threats.
Speaking alongside Prime Minister Takaichi, President Lee said that "the current international environment and trade order are unprecedentedly volatile." He added that "it is an urgent task of our time to deepen bilateral relations.”
Bilateral cooperation has never been more urgent. As the threat to the regional status quo grows, ever-increasing cooperation between Seoul and Tokyo — regardless of historic tensions — is the most pragmatic course forward.
South Korea may not be the primary front in China’s ambitions to rewrite the Indo-Pacific order, but it’s beginning to feel the pressure; and just like in the South China Sea, Beijing is finding innovative methods below the threshold of military confrontation to test Seoul’s commitment to defending its sovereignty.
China’s Shenlan 1 and Shenlan 2 fish farms — giant steel cages extending far below the surface of the ocean — can breed thousands of tons of salmon per year. But they’re also suspiciously familiar to tactics deployed in the South China Sea, where China has constructed the so-called "Great Wall of Sand" of artificial islands to encroach into the territorial waters of Vietnam, Taiwan and other regional powers.
Crucially, Shenlan 1 and Shenlan 2 sit in a Yellow Sea zone South Korea regards as its Exclusive Economic Zone but has jointly administered with China since a 2001 agreement.
Japan has also been subject to a dramatic recent escalation in Chinese pressure. In December last year, Chinese fighter jets locked radar on Japanese aircraft, a move that can signal a potential kinetic attack. Just one month later, China imposed export controls on Japan that target more than 800 dual-use goods, including rare earth elements and magnets. China's moves came after Takaichi signaled to the Japanese parliament that a Chinese attack on Taiwan could be considered a “survival-threatening situation,” a legal category that would allow "the deployment of Japanese troops."
During the recent Nara summit, and in response to such coercive measures, Lee and Takaichi pledged to expand bilateral cooperation on industrial supply chains and advanced technologies.
Both governments also recognize that stability in the Taiwan Strait is inseparable from their national and economic security. Indeed, any interference in the Taiwan Strait, or with Taiwan directly, poses a threat to the trade flows that sustain both economies.
As a precautionary measure, Japan, with the support of the United States, is expanding the presence of its forces across the Nansei island chain, which stretches from Okinawa toward Taiwan.
This was announced following a meeting between US Secretary of War Pete Hegseth and Japanese Defense Minister Shinjiro Koizumi, who confirmed that Tokyo and Washington are “cooperating closely.” The Defense Ministers also agreed to further enhance their joint deterrence and response capabilities, particularly by expanding training and defense-industrial cooperation.
For Japan and South Korea alike, proximity to potential flashpoints heightens the need for coordinated operational planning. This is the case for Taiwan and North Korea, where both Tokyo and Seoul share a convergent view of the threat posed by Pyongyang.
Denuclearization and missile deterrence remain core priorities for both countries. The operational dimension of this alignment is evident in the real-time trilateral missile data-sharing mechanism established in December 2023, integrating the US, South Korea and Japan in early warning and tracking of North Korean projectiles.
This system represents a shift from episodic bilateral coordination toward a more comprehensive deterrence architecture, embedding Tokyo and Seoul within a multilateral security framework. Trilateral cooperation also extends well beyond intelligence sharing. The Freedom Edge 2025 exercises, involving the US alongside Japan and South Korea, focused on ballistic missile defense and refining joint operational interoperability, ensuring the nations can respond to any threat rapidly and with sufficient force.
Underlying these security and economic imperatives is a vision that places the region’s stability and long-term prosperity at its core. Japan’s Free and Open Indo-Pacific vision provides the guiding architecture for regional coordination. FOIP promotes freedom of navigation and national sovereignty, while opposing unilateral changes to the status quo.
The Indo-Pacific security environment is rapidly deteriorating. China’s economic coercion and military assertiveness, as well as North Korea’s nuclear and missile advances, are converging to heighten risk.
Japan and South Korea now face an increasingly aligned set of vulnerabilities and responsibilities. Deepened bilateral cooperation, reinforced through trilateral mechanisms, is essential to sustaining a Free and Open Indo-Pacific through deterrence.
The urgency that Lee articulated in Nara reflects today’s reality: Now more than ever, regional security threats make Japan-South Korea cooperation essential.
Lee Byung-jong
Lee Byung-jong is a former Seoul correspondent for Newsweek, The Associated Press and Bloomberg News. He is a professor at the School of Global Service at Sookmyung Women’s University in Seoul. The views expressed here are the writer’s own. — Ed.
khnews@heraldcorp.com
