From Rivalry to Cooperation: Japan and South Korea in the Emerging Regional Order

João Pedro Nascimento

Relations between Japan and South Korea have undergone a process of significant reconfiguration since 2025, marked by the consolidation of a cooperation agenda amid the persistence of longstanding historical and territorial disputes. Unlike previous cycles, characterized by successive diplomatic crises related to the memory of the Japanese occupation, controversies over wartime compensation, and the dispute over the Dokdo/Takeshima islands, the current governments have sought to compartmentalize these differences and prevent them from dominating the entire bilateral agenda.

The arrival of Lee Jae Myung to the South Korean presidency initially raised concerns in Tokyo, largely due to the progressive leader’s history of criticizing the Japan policy pursued by previous administrations. Similarly, the rise of Sanae Takaichi to the office of Prime Minister of Japan generated uncertainty in Seoul because of her nationalist positions and her ideological proximity to the legacy of Shinzo Abe. Nevertheless, both governments quickly demonstrated a pragmatic approach, guided by national strategic interests and the deterioration of the international environment.

As a result, a process of political normalization has taken shape based not on the resolution of historical conflicts but on the creation of mechanisms capable of preventing those conflicts from undermining cooperation in areas considered priorities. This development represents an important qualitative transformation in bilateral relations, as the relationship has become increasingly driven by issues related to regional security, technological competition, and economic stability.

The main driving force behind this process is the worsening security environment in East Asia. The continuation of North Korea’s nuclear and ballistic missile programs, the strengthening of the strategic partnership between Russia and North Korea, China’s growing assertiveness in the Indo-Pacific, and uncertainties regarding the future level of U.S. commitment to its regional allies have created unprecedented incentives for closer ties between Tokyo and Seoul. Within this context, trilateral cooperation among Japan, South Korea, and the United States has assumed a central role in the regional deterrence architecture. Joint statements issued by the three countries emphasize their commitment to strengthening collective defense, strategic coordination, and the capacity to respond to threats posed by North Korea, including its nuclear and missile programs, cyber activities, and mechanisms for circumventing international sanctions.

As a consequence, an increasing process of institutionalization of defense cooperation can be observed. Regular meetings between defense ministers, joint military exercises, permanent working groups, strategic consultations, and the commitment to holding annual meetings demonstrate that cooperation is assuming a permanent character. This institutionalization reduces dependence on the individual preferences of political leaders and enhances the predictability of bilateral relations.

At the same time, the security agenda has expanded beyond strictly military issues. The growing importance of cybersecurity, the protection of critical infrastructure, artificial intelligence, digital governance, and technological resilience reflects an expansion of the traditional concept of national security. Both Japan and South Korea recognize that their economic competitiveness and strategic security depend on the protection of highly sophisticated production chains and the preservation of their technological leadership.

Consequently, the concept of economic security has emerged as one of the principal pillars of bilateral rapprochement. Both countries possess highly industrialized economies that are dependent on energy imports and deeply integrated into global value chains, making them particularly vulnerable to geopolitical shocks. The partial disruption of energy flows from the Middle East, especially amid tensions surrounding the Strait of Hormuz, reinforced the need for joint mechanisms of energy cooperation and industrial coordination. Cooperation has expanded to include areas such as the diversification of suppliers, the strengthening of critical mineral supply chains, the joint development of emerging technologies, artificial intelligence, semiconductors, industrial security, and the coordination of trade policies.

From the South Korean perspective, this strategy offers an important domestic political advantage. By framing rapprochement with Japan as a pragmatic response to the challenges of global technological competition and geoeconomic transformation, the government reduces the political costs associated with the historical memory of Japanese colonial rule. Thus, cooperation is presented as a necessity arising from national interests and changes in the international environment.

Despite these advances, significant structural constraints remain. The dispute over the sovereignty of the Dokdo/Takeshima islands continues to be one of the principal sources of friction between the two countries. The South Korean government continues to respond officially to Japanese claims by protesting official documents, territorial museums, and political statements reaffirming Tokyo’s position regarding the archipelago. Likewise, disagreements related to historical memory, school textbooks, and visits by Japanese officials to the Yasukuni Shrine continue to generate distrust in Seoul. However, the principal change observed since 2025 lies in the growing ability to manage these disputes without provoking large-scale diplomatic ruptures.

Important strategic differences also persist between the two countries. For South Korea, the stability of the Korean Peninsula remains an existential priority, leading Seoul to maintain greater openness to dialogue with Pyongyang and to demonstrate interest in regional cooperation mechanisms that include China. Japan, in contrast, adopts a more rigid stance regarding North Korean denuclearization and prioritizes strengthening the strategic axis formed by the United States, Japan, and South Korea as the principal instrument of regional stability.

This asymmetry becomes particularly evident with regard to North Korea. While Tokyo emphasizes complete denuclearization and the immediate resolution of the issue of Japanese citizens abducted by the North Korean regime, Seoul tends to combine deterrence mechanisms with support for diplomatic initiatives aimed at building lasting peace on the Korean Peninsula. This represents a structural difference stemming from the distinct geographical positions and strategic calculations of each country.

Another factor favoring bilateral rapprochement is the gradual transformation of public perceptions. Younger generations in Japan and South Korea display significantly higher levels of mutual acceptance, influenced by expanding cultural exchanges and the global popularity of K-pop, Korean dramas, and Japanese popular culture. This social change reduces some of the political barriers traditionally associated with the bilateral relationship and creates a more favorable domestic environment for cooperation.

The growing institutionalization of diplomatic, military, and economic contacts represents another source of stability. Frequent meetings among foreign ministers, defense ministers, economic authorities, and technical working groups create permanent coordination mechanisms that reduce the risk of abrupt setbacks resulting from isolated crises or changes in government. The continuity of these channels demonstrates that cooperation is beginning to acquire its own institutional characteristics, becoming less dependent on domestic political circumstances.

From a geopolitical perspective, the rapprochement between Japan and South Korea forms part of a broader process of reorganization of the Indo-Pacific security architecture. The convergence between the two largest industrialized democracies in Northeast Asia strengthens the U.S.-led regional strategy of containing threats originating from North Korea while balancing China's growing projection of power. At the same time, it enhances both countries' capacity to respond jointly to transnational challenges related to energy, global supply chains, technological competition, and cybersecurity.

In summary, relations between Japan and South Korea since 2025 can be understood as a process of pragmatic convergence. Historical and territorial disputes remain unresolved and continue to constitute important sources of political tension. Nevertheless, they have ceased to prevent the expansion of cooperation in areas considered essential for the security and economic competitiveness of both countries. The bilateral partnership has thus become more resilient and institutionalized, supported by converging interests in defense, economic security, technological innovation, and regional stability, even though it remains marked by structural ambiguities and limitations arising from historical legacies and the differing geopolitical priorities of Tokyo and Seoul.

References:

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João Pedro Nascimento, holds a Bachelor's degree in International Relations and a postgraduate qualification in Public Policy. He has experience in business internationalization, international market expansion, international negotiations, and strategic partnership management. He works as a consultant in foreign policy and international economics and is also a partner at a financial advisory firm, connecting companies and investors with global opportunities through scenario analysis, risk assessment, and strategic planning. He is the founder of RI Talks, an independent platform dedicated to the analysis and discussion of national and international affairs.