Japan-Southeast Asia relations marked two milestones in 2023-24. The first was the 50th anniversary of Japan-ASEAN Relations, during which Japan and ASEAN emphasized an equal partnership by adopting the keyword “co-creation” to promote economic prosperity and security stability in Southeast Asia and beyond. The second is strengthening Japan-Philippines bilateral strategic ties, not only bilaterally, but also trilaterally with the United States and quadrilaterally with Australia. Japan continuously engages with other Southeast Asian states and strengthens ties with ASEAN to reinforce ASEAN Centrality and unity, yet a challenge remains: how Japan can design a regional architecture in East Asia and the Indo-Pacific by clarifying the roles and division of labor among those institutions.

50th Anniversary of Japan-ASEAN Friendship and Cooperation

Figure 1 Leaders pose for a commemorative photo at the Commemorative Summit for the 50th Year of ASEAN-Japan Friendship and Cooperation on December 17, 2023. Photo: The Government of Japan.

Japan and ASEAN held the Commemorative Summit for the 50th Year of ASEAN-Japan Friendship and Cooperation on Dec. 17, 2023. While Japan was not an ASEAN dialogue partner in 1973, the two began in-depth diplomatic engagements due to Japan’s synthetic rubber exports, which threatened Southeast Asia’s natural rubber industry. Given Southeast Asian suspicion of Japan stemming from the legacy of World War II, this dialogue did not originate from a positive relationship. However, over time, Japan and ASEAN member states cultivated positive partnerships through many initiatives, most notably the Fukuda Doctrine of 1977. The commemorative summit represents Japan’s regional engagements and its willingness to enhance this trend, building on previous commemorative summits in 2003 and 2013. 

At the summit, Japan reiterated its respect for ASEAN Centrality and unity, promising to mainstream the “ASEAN Outlook on the Indo-Pacific” (AOIP), and synthesizing Japan’s “Free and Open Indo-Pacific” and AOIP. At the same time, Japan and ASEAN introduced three new pillars to enhance relations: 1) “Heart-to-Heart Partners across Generations”; 2) “Partners for Co-creation of Economy and Society of the Future”; and 3) “Partners for Peace and Stability.” The first pillar focuses on human exchange, building on the Fukuda Doctrine’s aim of deepening a “heart-to-heart” understanding between Japan and Southeast Asian countries, expressing a resolution to further people-to-people exchanges in a variety of fields, including both intellectual and cultural exchanges. 

Through this shared vision, the Japan-ASEAN relationship entered a new phase in two significant ways. First and foremost, Japan and ASEAN recognized that they have become more equal partners politically and economically. Although similar areas of cooperation have been discussed over the past two decades, the new vision statement’s keyword, “co-creation,” emphasizes the importance of collaborative effort. ASEAN’s socio-economic developments have been remarkable, and Japan now relies more on these for its own peace and prosperity in fields such as business startups and human resources. In this context, “co-creation” implies a new relationship of truly equal partners. 

Second, Japan and ASEAN look beyond a bilateral relationship and show their intent to contribute to shaping a regional order in the Indo-Pacific region. This is represented by the “Partners for Peace and Security,” which calls of them “to promote a rules-based Indo-Pacific region that is free and open, [embracing] key principles such as ASEAN’s unity and centrality…” Previously, both focused specifically on improving Japan-ASEAN relations, but did not clearly state their international contribution through enhanced regional cooperation, albeit their consideration of regional and global security. Under the current strategic circumstances, they have begun to explore ways both can collaboratively contribute to international peace and stability in the Indo-Pacific.  

These shared interests and visions culminated in interactions between Japan and ASEAN in 2023. Given ASEAN’s institutional norm of “consultation and consensus,” Japan has comprehensively engaged with ASEAN members through track-1 and track-2, illustrating the recommendations produced by the Ministry of Foreign Affairs (MOFA) and the Ministry of Economic, Trade and Industry (METI). Functionally, Japan began to revitalize activities toward ASEAN. In the defense arena, Japan conducted the Fourth and Fifth Japan-ASEAN Ship Rider Cooperation for the first time in four years in March and September. Japan’s Ministry of Defense also launched a new concept, JASMINE (Japan-ASEAN Ministerial Initiative for Enhanced Defense Cooperation), under its “Vientiane Vision 2.0” in November. Japan pushed the establishment of the “Asia Zero Emission Community” (AZEC), aiming to achieve economic growth, energy transition, and decarbonization simultaneously, resulting in the AZEC Leaders’ Joint Statement. 

Meanwhile, Japan and ASEAN decided to elevate relations to the “Comprehensive Strategic Partnership,” following China, the United States, and Australia. While largely symbolic, this status indicates that their relationship is as important as other regional major powers, creating political momentum for furthering Japan-ASEAN functional cooperation. This underscores that ASEAN remains one of the most important diplomatic actors for Japan in the Indo-Pacific as the institution has been key to shaping a regional order. In the next phase, it is important to see the extent to which Japan and ASEAN can follow through the broad range of implementation plans for the next decade. 

Emergence of New Bilateral, Trilateral, and Quad (“Squad”): The Philippines

In 2023-24, the Kishida administration focused on the enhancement of Japan’s strategic relationship with the Philippines. When Ferdinand Marcos Jr. became president in 2022, taking over from the China-leaning Rodrigo Duterte, the Philippines attempted to strike a delicate balance in its relationship with China and the United States. This posture became increasingly difficult as China’s assertive behavior in the South China Sea continued, particularly in regard to Second Thomas Shoal and the Scarborough Shoal. ASEAN and China’s negotiations over the Code of Conduct in the South China Sea have been slow and insufficient to deter unilateral actions or the creation of fait accompli by claimant states. ASEAN members have long faced difficulty in maintaining a united front, frustrating the Philippines, and as Japan faces a similar security situation in the East China Sea, both Japan and the Philippines have deepened strategic cooperation in three ways. 

First, Japan and the Philippines began to facilitate closer bilateral engagement. In February 2023, Prime Minister Kishida and President Marcos issued the “Japan-Philippines Joint Statement,” envisioning coordination and cooperation on infrastructure development, disaster management, energy transformation, security cooperation. This includes the Foreign and Defense Ministerial Meeting (2+2), the Vice-Ministerial Strategic Dialogue, and a variety of joint military exercises such as Japan’s participation in the Philippines-US “KAMANDAG” and “SAMA-SAMA” exercises, as well as Japan’s provision of coastguard cutters to the Philippine Coast Guard (PCG). On Nov. 4, Kishida visited the Philippines and made a speech at the Joint Session of the Philippine Senate and House of Representative, “Heart-to-heart ties for the Next Generation,” referencing the Fukuda Doctrine initiated in Manila in 1977. Kishida attempted to advance this doctrine for promoting Japan’s relations with ASEAN, explaining Japan’s four pillars of the new plan for a FOIP. At the same time, he emphasized Japan’s initiative to comprehensively engage with the Philippines through the Official Security Assistance (OSA), infrastructure development, decarbonization, and trilateral cooperation with the United States. The summit meeting also highlighted the commencement of the negotiations on a Japan-Philippines reciprocal access agreement (RAA).

Second, Japan and the Philippines intensified trilateral cooperation with the United States. Beginning with the first-ever trilateral coast guard joint exercise in June 2023, and sharing strategic perspectives in the Indo-Pacific, particularly on the South China Sea, a series of trilateral meetings were held in 2023 and 2024. There were five important formal and informal meetings for policy coordination: the Trilateral National Security Advisors meeting on June 16, 2023, the Trilateral Foreign Ministers’ Meeting on July 14, 2023, the Informal Meeting between Prime Minister Kishida, President Marcos, and US Vice President Kamala Harris on Sept. 6, 2023, another Foreign Minister’s Meeting on Sept. 22, 2023, and the Trilateral Vice Ministers’ Meeting on March 21, 2024. These efforts culminated in the Trilateral Summit on April 11. 

Figure 2 The first meeting of the Japan-Philippines-US Trilateral Summit on April 11, 2024. Photo: Prime Minister’s Office of Japan.

This summit demonstrated their commitment to comprehensive cooperation, resulting in several tangible outcomes, such as the launching the Luzon Economic Corridor—the first economic corridor in the Indo-Pacific under the “Partnership for Global Infrastructure and Investment Partnership” promoted by G7—the establishment of the trilateral Cyber and Digital Dialogue, and regularization of joint exercises and training between three coastguards as well as between defense forces. 

Third, new quadrilateral cooperation between Japan, the Philippines, Australia, and the United States, informally called “the Squad,” began to emerge. In June 2023, the four defense ministers held the first ministerial meeting alongside the Shangri-La Dialogue. Although this was ad-hoc and there was no commitment to regularize the ministerial meeting, their defense cooperation and regular interactions gained political momentum as their bilateral and trilateral relationships developed. A quadrilateral joint naval exercise was conducted in April 2024, and subsequently, in May 2024, the second quadrilateral defense ministers’ meeting was held in Hawaii. This meeting issued a joint readout, indicating that the four shared security concerns over the East and South China Seas, particularly regarding China’s actions despite the “final and legally binding 2016 South China Sea Arbitral Tribunal Award.” 

Figure 3 The second meeting of the Japan-Philippines-US Trilateral Summit on April 11, 2024. Photo: Prime Minister’s Office of Japan.

These efforts aim to nurture networks of the US “hub-and-spokes” system, which US National Security Advisor Jake Sullivan has termed the “latticework of cooperation.” US allies, including Japan, Australia, and the Philippines, are strengthening bilateral and trilateral strategic cooperation to independently bolster defense capabilities and align to aggregate defense and deterrence capacities in the Indo-Pacific region. Nevertheless, those frameworks have only recently emerged and have yet to be institutionalized or formalized, allowing room for evolution. 

In fact, although the four share similar strategic perspectives, they do not necessarily align completely. For instance, the Taiwan issue has been a prominent topic in dialogues, yet the extent of cooperation among US allies remains unclear. Their policies toward the South China Sea have been more coordinated. Consequently, there is potential for these relationships to evolve into either an AUKUS-like strategic minilateralism or a Quad-like functional minilateralism. In addition, an important challenge lies in determining how these frameworks will align with ASEAN. Despite expressing respect for ASEAN Centrality and unity, clarifying the institutional division of labor with ASEAN and ASEAN-led institutions would be imperative to assure other ASEAN member states in the future. 

Japan’s Comprehensive Engagement through the “Free and Open International Order”

Japan’s Southeast Asian policy exhibits strong continuity as well, especially when it comes to active bilateral engagements. Japan’s diplomatic, economic, and defense engagements with other Southeast Asian states remained constant. The only notable change in Japan’s diplomatic approach was a slight shift in strategic narratives. Since 2016, Japan has been promoting the “Free and Open Indo-Pacific” narrative at the international stage, including Southeast Asia. However, given the prolonged war between Ukraine and Russia and increasing uncertainty about the conflict between Israel and Hamas, along with diverging perspectives on them among the Global South, it became clear that an international order is not solely shaped by events only in the Indo-Pacific region. Therefore, while the Indo-Pacific region remains central to Japan’s strategic focus, the Japanese government began to emphasize not only the FOIP but also the “Free and Open International Order based on the Rule of Law (or International Law)” in engagements with Southeast Asian countries. This shift became more pronounced in the second half of 2023. 

In this context, Japan diplomatically reinforced its bilateral relationship with Southeast Asian states by upgrading its ties with several states to “comprehensive strategic partnerships,” generally on significant anniversaries. While ASEAN and Japan concluded the ASEAN-Japan Comprehensive Strategic Partnership in September 2023, these bilateral partnerships include a “Comprehensive Strategic Partnership” with Cambodia in January 2023 at the occasion of the 70th anniversary of Japan-Cambodia diplomatic relations; a “Comprehensive and Strategic Partnership” with Indonesia in December 2023 at the occasion of the 65th anniversary of Japan-Indonesia diplomatic relations; a “Comprehensive Strategic Partnership” with Malaysia in December 2023; and a “Comprehensive Strategic Partnership for Peace and Prosperity in Asia and the World” with Vietnam in November 2023 at the occasion of the 50th anniversary of Japan-Vietnam diplomatic relations. Also, as Japan and Brunei approached the 40th anniversary of their diplomatic relations in 2024, plans were made to elevate relations to a “strategic partnership.”

Consequently, among the 10 ASEAN member states, only three member states do not have strategic partnership relations with Japan: Myanmar, Brunei, and Singapore. Japan’s engagement with Myanmar faces diplomatic difficulties because of the 2021 military coup. Brunei is now considering elevation of its relationship with Japan, and Singapore already has substantial diplomatic, economic, and defense ties with Tokyo, exemplified by the Japan-Singapore Partnership Programme for the 21st Century (JSPP21), the Japan-Singapore Economic Partnership Agreement, and the Agreement of the Japan-Singapore Defense Equipment and Technology Transfer. While no clear set of characteristics defines strategic partnerships, making it sometimes difficult to ascertain the strategic depth of these relationships, the designation nonetheless provides opportunities for Japan and Southeast Asian states to hold high-level meetings, engage comprehensively with each other at different levels, and legitimatize their relationships to avoid overdependence on any particular great power. 

Economically, Japan’s recent focus has been on the establishment of the AZEC, which includes Australia and all ASEAN members except for Myanmar. This initiative reflects a broad understanding of the decarbonization process, encompassing issues from critical minerals and infrastructure development to critical and emerging technologies. While regional collaboration through the AZEC is essential for facilitating this process in Southeast Asia and East Asia, diverse levels of economic development in each regional state make bilateral engagements crucial for addressing specific needs such as human development, technology transfer, and rules-making dialogues. In this connection, Japan introduced the “Co-Creation for Common Agenda Initiative,” based on the revised Development Cooperation Charter in June 2023. This initiative aims to set development goals and create realistic plans alongside Southeast Asian states and their private sectors. Under this scheme, Japan has agreed to cooperate in the digital sector with Cambodia and agricultural sector with Thailand. 

Japan has revitalized its defense diplomacy in Southeast Asia through capacity-building programs and OSA. Japan conducted the fourth and fifth Japan-ASENA Ship Rider Cooperation Program, as mentioned above. Between May 2023 and April 2024, it offered 12 capacity building programs to Southeast Asian states, including Timor Leste, covering various fields, such as cyber security, humanitarian assistance/disaster relieve (HA/DR), civil engineering, Japanese language training, underwater UXO clearance, and vessel maintenance. Additionally, as an annual exercise, Japan conducted the Indo-Pacific Deployment 2023 (IPD23) by dispatching maritime self-defense force fleets, including JS Izumo, JS Samidare, and JS Shiranui, to participate in Indo-Pacific naval exercises and port calls in Southeast Asian states, namely Malaysia, Indonesia, the Philippines, Singapore, and Vietnam. 

Furthermore, Japan has begun to use OSA to provide military equipment to boost the capabilities of partner states in the region, although it does not intend to provide lethal weapons. In 2023, Japan identified the Philippines and Malaysia along with Bangladesh and Fiji as priority recipients of OSA and included Vietnam in November. Assistance included the provision of coastal radars to the Philippines and rescue boats to Malaysia to enhance their maritime domain awareness. Although the OSA budget for fiscal year 2023 was modest—providing approximately $4 million to the Philippines and $2.5 million to Malaysia—it is subject to change, depending on Japan’s economic situation and demands from Indo-Pacific states. 

Japan continues to utilize Official Development Assistance (ODA) to empower law-enforcement capabilities of Southeast Asian states. For example, in December 2023, Japan exchanged the note to provide a large patrol vessel to the Indonesian Coast Guard Agency. However, ODA remains primarily focused on socio-economic development and is characterized as non-security-oriented assistance. Although patrol ships can be provided through ODA, no military equipment is transferred under this arrangement. OSA was launched to complement ODA by addressing security needs that ODA does not cover.  

Among these cooperative efforts, Myanmar remains an outlier. Japan has suspended formal diplomatic interactions with Myanmar since the 2021 coup, although it regularly provides humanitarian aid through international organizations and nongovernmental organizations and cooperates with ASEAN. Instability in Myanmar has also impacted Japan’s broader Southeast Asian engagement, such as the Japan-Mekong Cooperation, which consists of Japan and all Mekong countries, including Myanmar, and has not convened since 2021. 

Southeast Asian Perceptions toward Japan 

It is widely recognized that Japan is the most trusted major power in the Indo-Pacific region among ASEAN member states. According to “The State of Southeast Asia: 2024 Survey Report,” an annual survey conducted by the Yusof-Ishak ISEAS, Japan consistently ranks as the most trusted among other major powers, such as the United States, the EU, China, and India. Since the survey’s inception in 2019, Japan has maintained this top position, illustrating its success in engaging Southeast Asia positively despite the historical legacy of World War II. However, there are two caveats to consider. 

First, Japan is not perceived as a strategic threat to Southeast Asia, either economically or strategically. The ISEAS Survey shows that while Japan is ranked fourth in terms of economic influence—following China, ASEAN, and the United States—and similarly in political and strategic influence, there is a significant gap between Japan and the top three, China, the United States, and ASEAN. More specifically, Japan scored 3.7% in terms of economic power compared with China’s 59.5%, ASEAN’s 16.8%, the United States’ 14.3%. In political and strategic terms, Japan also scored 3.7%, while China, the US, and ASEAN scored 43.9%, 25.8%, and 20%, respectively. These figures suggest that from ASEAN’s perspective, Japan lacks the material capabilities to significantly influence the region. Still, Japan’s continual engagement has consolidated its position as the most trusted state, though the primary players in the region remain China, the United States, and ASEAN. 

Second, being the “most trusted country” does not necessarily mean that Japan is considered a strategic option for ASEAN member states. Survey responses indicate a trend where Japan is not seen as the leading force in maintaining a rules-based order or upholding international law; these roles are more likely attributed to the United States (27.9%), ASEAN (26.9%), the EU (16.9%), and even China (11.5%), with Japan ranking far behind (8.8%). Furthermore, when participants were asked to identify which actor could be considered a “third party” in the context of the US-China strategic competition, the EU was preferred (37.2%) over Japan (27.7%). It is quite understandable that the EU is viewed more favorably by ASEAN members, given its multilateral nature and representation of multiple states. However, countries such as Brunei, Indonesia, and Singapore still regard Japan as the preferred third party. This preference may be less about Japan’s material and strategic capacities and more about its considerable soft power as it is the second most favored place to live or work and tops the list as the most popular place to visit.  

These survey results position Japan uniquely in Southeast Asia—strategically harmless, economically beneficial, and culturally attractive. Although Japan’s strategic importance may not match that of other major powers, namely the US and China, it is more diplomatically accessible to ASEAN members. This accessibility stems from Japan’s traditional focus on socio-economic engagement. However, Japan has been gradually assuming a more active security role in empowering Southeast Asia. For example, since the 2010s, Japan has concluded defense equipment and technology transfer agreements with six ASEAN members: Indonesia, Malaysia, the Philippines, Singapore, Thailand, and Vietnam, and invented OSA to grant defense equipment. Japan may play a more strategic part in ensuring stability in Southeast Asia in the future. 

Looking Ahead

From 2023 to 2024, Japan made progress in two significant areas: celebrating the 50th anniversary of ASEAN-Japan relations and enhancing ties with the Philippines, showcasing both traditional and new approaches. On the one hand, Japan reaffirmed its commitment to Southeast Asia and ASEAN, moving beyond mere socio-economic assistance to emphasize an equal partnership aimed at advancing regional stability and prosperity in Southeast Asia and beyond. On the other hand, recognizing the limitations of existing institutional frameworks to adequately address regional tensions and confrontation in areas such as the East and South China Seas and the Taiwan Strait, Japan actively engages with regional states, particularly US allies. From May 2023 to May 2024, Japan, along with the United States, focused on the Philippines, nurturing the Japan-US-Philippine trilateral framework as well as the new Quad with Australia. 

This evolving diplomatic engagement contributes to gradual changes in a regional architecture of Southeast Asia, East Asia, and the Indo-Pacific. However, managing these new institutional frameworks poses several challenges. One issue is their lack of consolidation or formalization, which leaves room for institutional evolution. As with the evolution of the “Quad,” other new frameworks such as the “Squad” may shift objectives and functionalities. While the strategic environment’s fluidity makes flexibility advantageous, excessive ambiguity could undermine the strategic and functional validity of these frameworks. 

Another issue is how these new arrangements would impact ASEAN, particularly in terms of ASEAN Centrality. These new frameworks have been created to manage regional challenges that existing institutions, including ASEAN and ASEAN-led mechanisms, cannot manage. That said, without clear communication, ASEAN might view these developments as undermining its diplomatic influence in East Asia and beyond. This is particularly so given Japan’s growing role in strategic affairs in the Indo-Pacific region and its efforts to counter China’s assertiveness. 

Looking ahead, Japan’s engagement with Southeast Asia from 2024 to 2025 will unlikely undergo abrupt changes. The major variable for Japan in 2024, the result of the US presidential election in November, will certainly impact alliance politics and management. Nevertheless, Japan-Southeast Asia relations are expected to maintain their course unless a larger structural shock occurs. The task for Japan in 2024-25 is to articulate a vision for a new regional architecture in East Asia and the Indo-Pacific, leveraging its unique position to reassure ASEAN and strengthen ties with Southeast Asia.