[New Year Special Commentary Series] ③ Japan's Foreign Policy Plan B in 2026 and ROK-Japan Relations: Between Dependence on the U.S. and Conflict with China

I. Introduction

Japan, while dedicating considerable effort to stabilizing U.S.-Japan relations immediately after the launch of the second Trump administration, even amidst ridicule for its appeasement diplomacy, reached the conclusion that it could not entirely rely on the U.S. for its security following the humiliating tariff negotiations in September. The U.S. "National Security Strategy (NSS 2025)" released in December reaffirmed this perception. It starkly revealed that the U.S. no longer possesses the will to fulfill its responsibilities as a hegemonic power, such as pursuing global agendas or contributing to maintaining order, and is instead focused on homeland defense and managing the Western Hemisphere. Furthermore, it showed a softened stance towards China, whose threat perception has been escalating in conflict with Japan. Japan realized that this was a significant departure from the Biden administration's characterization of China as a revisionist power seeking to reshape the international order and its sole strategic competitor.

Japan's disappointment with NSS 2025 has led to discussions about a shift in its existing foreign policy. As a proactive response to power rebalancing, strategic considerations are emerging, including rebalancing towards a proper interdependent relationship with the U.S., strengthening its own defense capabilities, expanding cooperation with like-minded countries (South Korea, Australia, NATO, etc.), and enhancing strategic communication with China. These discussions are expected to accelerate following the U.S. military intervention to oust President Maduro in Venezuela on January 3rd. The trajectory will depend on the domestic political dynamics within Japan regarding the U.S. stance aimed at solidifying dependence on the U.S., and the development of China-Japan relations, which have been strained by Prime Minister Takaichi's remarks on Taiwan. Will the U.S.-Japan tariff agreement and defense cost-sharing agreement, the deterioration of China-Japan relations, and China's coercive diplomacy lead to a Plan B for Japanese foreign policy? What impact will it have on ROK-Japan relations? Will the trend of improving bilateral relations, driven by the sustained positive mutual perceptions between the peoples of South Korea and Japan since 2020 and reinforced by government-level efforts (top-down), continue in 2026? What are the variables?

II. U.S.-Japan Relations Amidst Rising Distrust of the U.S.

The greatest challenge facing Japanese diplomacy in 2025 was to stabilize U.S.-Japan relations within the framework of the power rebalancing strategy pursued by the second Trump administration. The second Trump administration seeks to transfer as many obligations as possible to allies and partners while retaining the rights and benefits of a hegemonic power. It aims to restore the economic foundations of hegemony by monopolizing the exorbitant privilege of dollar hegemony and mobilizing tariffs as a key tool, while refraining from external military interventions and shifting the burdens of hegemony, such as increased defense spending and burden-sharing by allies and control over advanced technologies, onto them.

Japan's initial foreign policy stance was to act as a partner assisting the U.S. in restoring and maintaining its hegemonic order. Through the Abe and Kishida administrations, Japan expressed its intention to alleviate the U.S. burden by strengthening its military capabilities and the U.S.-Japan alliance in security matters, and to actively provide public goods for international stability and peace by engaging with the Global South, including Southeast Asia and India (Yeo Han-goo, 2024). This can be considered the fundamental "Plan A" of Japanese foreign policy.

With the advent of the second Trump administration, Japan's greatest concern was the possibility of the U.S. falling into isolationism or losing international trust and leadership through contradictory and self-destructive actions. The scenario envisioned was that if the Trump administration repeatedly imposed reckless tariffs, undermined alliances, frequently changed policies, and violated international rules and norms while asserting its hegemonic rights, the risk of declining trust and defection by allies would increase, accelerating the decline of U.S. hegemony and leading to a "world without the U.S." In such a vacuum, China and Russia would expand their influence. Therefore, if Plan A, the hegemonic follower line, fails to function, the necessity of establishing a "Plan B" arises. The need for the latter has generally intensified through the following three stages:

The first stage involved statements by Secretary of State Mark Rubio and Vice President J.D. Vance early in the year. In his confirmation hearing, Rubio declared his intention to pursue an "America First" foreign policy within a multipolar international order, rather than a U.S.-centered liberal international order. Subsequently, at the Munich Security Conference, Vance expressed a negative stance on U.S. security commitments to Europe. These statements were interpreted as evidence that the U.S. no longer possessed the will to fulfill its role as a hegemonic power. Consequently, a perception emerged that preparations must be made for a scenario where the U.S. significantly reduces its security commitments, including alliance and extended deterrence, international development aid, and cooperation on climate change, beyond abandoning free trade (Kojo Yoshiko et al., 2025).

The second stage involved the U.S.'s transactional and coercive approach towards its allies during bilateral negotiations. Prime Minister Shigeru Ishiba, aiming to foster stable U.S.-Japan relations, presented a substantial investment pledge of $10 billion during a summit meeting shortly after the launch of the second Trump administration in February. However, he expressed bewilderment and disappointment when President Trump announced large-scale tariff measures in April (25% tariffs on steel and aluminum, 25% tariffs on automobiles and auto parts, and a 24% reciprocal tariff). He even described Japan as being toyed with, calling it an act that disregarded courtesy towards allies. During negotiations, President Trump pressured Japan to significantly increase its defense spending, criticizing its free-riding on security. Despite the Kishida government's declaration in 2022 to increase defense spending from 1% to 2% of GDP by 2027, Secretary of Defense Hagges demanded a 3.5% increase, shocking relevant authorities. Ultimately, a humiliating tariff agreement was reached on September 4th, reducing the reciprocal tariff rate to 15% in exchange for a commitment of approximately $550 billion in investments to the U.S. The bitter lesson Japan learned from this was that it should not rely entirely on the U.S. for its security. In negotiations with Trump, who viewed alliances as transactions, Japan keenly felt that its structural vulnerability of over-reliance on the U.S. in security matters was leading to an asymmetry in economic bargaining power.

The third stage is the NSS 2025 released in December. The declaration to reduce external intervention, engage only in cases of clear U.S. core interests, and prioritize homeland and Western Hemisphere management is akin to a sphere of influence concept. As seen in the U.S. attack on Venezuela, sphere of influence policies justify actions by great powers that restrict the effective sovereignty of countries within the region. In the Americas, actions lacking clear legal basis under international law may become frequent, justified by the need to curb immigration, transnational crime, and Chinese infiltration, and to secure strategic locations. Indeed, following the series of events on January 3rd, including the U.S. attack on Venezuela, the apprehension of its president, and the declaration of Venezuela's "operation," the Japanese government issued a principled response respecting fundamental values such as democracy and international law principles. However, it keenly felt that the fundamental principles of Japanese diplomacy, such as the rule-based international order represented by the "Free and Open Indo-Pacific (FOIP)" and value-based diplomacy, were completely disregarded.

Furthermore, this report lacks a definition of threat actors (Jeon Jae-seong, 2026). This is why there are reactions from the Japanese side that the report reassures adversaries like China and Russia while discouraging allies (Ishii Masafumi, 2025). Of course, the U.S. claims it does not recognize China's sphere of influence in the Indo-Pacific region and asserts its role in checking China's hegemonic influence, while emphasizing collective defense efforts among allies to build defense capabilities along the first island chain in the Western Pacific. However, the overall emphasis is on China as an economic competitor, a partner for rebalancing trade with the U.S., and for securing critical supply chains and strategic materials. The threat perception towards China is significantly weaker compared to the Biden administration, which defined China as the "sole strategic competitor on Earth." Japan cannot help but feel anxiety and doubt about an alliance relationship based on shared threat perceptions.

For these reasons, discussions about Plan B, a contingency for when Plan A—which presupposes U.S. hegemony or the possibility of its restoration—fails, are actively underway within Japanese political and academic circles.

III. Japan's Plan B

For U.S. allies, the discussion of Plan B ultimately boils down to securing strategic autonomy. In Europe, Plan A involves strengthening NATO by increasing defense budgets and confirming U.S. commitments, while Plan B focuses on achieving strategic autonomy through self-reliance without U.S. military intervention. However, Japan's situation is different. Unlike Europe, which possesses the capability to achieve military balance with Russia, Japan faces difficulties in achieving military self-reliance to balance against its strategic competitor, China. Most importantly, there is no alternative to the extended deterrence provided by the U.S. Domestic support for "anti-nuclear" sentiment also remains strong. According to an EAI-API public opinion poll conducted in August 2025, 67.5% of South Koreans support acquiring their own nuclear weapons, whereas the figure for Japan is only 23.7% (Yeo Han-goo et al., 2025).

Therefore, to counter China's strategic influence and maintain a free and open international order, it is considered unrealistic to seek an international order without the U.S., as there is currently no alternative besides the U.S. In this regard, Japan's Plan B for foreign policy is oriented towards reducing over-reliance on the U.S. (and China) by enhancing its military and diplomatic capabilities, thereby achieving a state of proper interdependence and fostering strategic autonomy within that framework, moving away from a policy of appeasing the U.S. based on distrust (Akita Hiroyuki, 2024; Mori Satoshi, Hosoya Yuichi, Tsuruoka Michito, 2025; Sahashi Ryo, 2025). While Plan A presupposes the restoration and maintenance of U.S. hegemony, Plan B discussions view this skeptically and are closer to a de-risking strategy towards the U.S. by reducing dependence. Thus, if Plan A defines Japan's role in U.S.-Japan relations as a complementary partner to the U.S., Plan B appears to aim for indispensability within a network of interdependence—an irreplaceable node. In terms of security, if Plan A pursues strategic flexibility through military buildup, Plan B seeks strategic autonomy through military buildup. In economic security, Plan B aims to enhance strategic autonomy by protecting key industries and securing infrastructure safety nets, and to achieve strategic indispensability that provides deterrence or bargaining power against coercion or retaliation from the U.S. and China by fostering core industries and technologies. In diplomacy, while Plan A involves strengthening security cooperation with like-minded countries through small multilateral frameworks centered around the U.S. (e.g., U.S.-Japan-Australia, ROK-U.S.-Japan, U.S.-Japan-Philippines, and the Quad), Plan B expands security cooperation without the U.S. to include Australia, South Korea, the Philippines, New Zealand, and NATO member states, while also encompassing the task of securing strategic communication with China. The expansion of the Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTPP) is particularly recognized as a measure to diversify over-reliance on the U.S. in the mid- to long-term and as an element that could enable Japan to lead a "multilateral order without the U.S."

Table 1. Plan A and Plan B of Japanese Foreign Policy

IV. The Takaichi Administration's Dilemma: Between Dependence on the U.S. and Conflict with China

When forecasting Japan's foreign policy in 2026, a key point of observation will be Japan's strategic choices regarding its relationship with a Trump-led United States. Fundamentally, the U.S. seeks to maintain an asymmetrical advantage in negotiations by leveraging Japan's excessive dependence on it. While urging Japan to strengthen its military capabilities, the U.S. aims to expand arms exports and advance the integration of command and control between its military and Japan's Self-Defense Forces, thereby maintaining and reinforcing Japan's dependence on the U.S. Simultaneously, it demands that Japan play a crucial role in the collective defense of the First Island Chain to protect maritime transport routes in the Taiwan Strait and the South China Sea. In economic terms, the U.S. also seeks to expand and deepen the network of U.S.-Japan interdependence. Japan is being guided to ensure that its direct investment in the U.S. (approximately $550 billion) plays a central role in expanding its infrastructure, securing its manufacturing base, and promoting employment. In essence, the U.S. aims to maximize its security and economic interests by exploiting this asymmetrical interdependence. Therefore, the U.S. favors Japan's Plan A.

In this context, Plan B could present a significant political burden for the Такаichi administration, which took office last October. As the head of a conservative coalition government that values alliances, Prime Minister Такаichi considers maintaining stable relations with the Trump administration and his close personal relationship with President Trump as political assets. Consequently, a shift from the established course (Plan A) to a course that relatively emphasizes strategic autonomy (Plan B) requires political persuasion and support. Prime Minister Такаichi must be able to politically persuade the public that Plan B is not a path to Japanese self-reliance akin to that advocated by the right-wing politician Shintaro Ishihara, who caused a sensation with his book "The Japan That Can Say No," and that Plan B is a gradual, long-term evolutionary process from Plan A. To achieve this, a sophisticated vision and roadmap for the transition must also be developed.

Another variable is the external factor of Sino-Japanese conflict. Prime Minister Такаichi's remarks regarding Taiwan in the Diet on November 7th sharply worsened Sino-Japanese relations. The statement suggested that if a Taiwan contingency occurred and the U.S. intervened, leading to China attacking U.S. forces, Japan could recognize it as a "situation threatening Japan's existence" and exercise its right to collective self-defense. A "situation threatening Japan's existence" is defined as a situation where an armed attack on an allied nation threatens Japan's existence; previous Japanese governments had avoided answering specific cases to prevent diplomatic friction with neighboring countries. However, Prime Minister Такаichi, as a hardliner towards China, revealed her true intentions, triggering the incident. China, viewing this as an infringement on its core interests, demanded the retraction of the statement and strongly protested. Following economic retaliatory measures such as a travel warning to Japan and a ban on imports of Japanese seafood, China engaged in a propaganda war reminiscent of past wolf warrior diplomacy. It then escalated to military threats, with Chinese aircraft carrier-based aircraft targeting SDF fighter jets with radar, and carrier-based aircraft entering Japan's Air Defense Identification Zone (ADIZ) on the 30th, flying jointly with Russian bombers around Japan, thereby increasing military pressure in the vicinity of the First Island Chain.

In fact, Prime Minister Такаichi had approached the summit with Chinese President Xi Jinping on October 31st with the stance of inheriting the Abe administration's approach to China, "strategic mutually beneficial relationship," aiming to build a "constructive and stable relationship as important neighbors." President Xi Jinping had also supported stabilizing relations. As overt U.S. prioritization became apparent, China elevated its neighborhood diplomacy to a central pillar of its strategy to stably secure influence in the surrounding region. Accordingly, alongside efforts to improve relations with Australia and South Korea, China considered taking forward-looking measures regarding Japanese seafood, imports of which had been suspended due to the Fukushima nuclear wastewater issue, and pursued a temporary visa exemption policy for Japanese tourists visiting China.

As this atmosphere of cooperation turned into conflict and the situation escalated, Prime Minister Такаichi stepped back on November 11th, stating, "I regret making remarks assuming specific scenarios." On December 16th, she further retreated, saying, "I believe it is a part that needs reflection that my remarks were perceived as going beyond the existing government position." Nevertheless, the likelihood of Prime Minister Такаichi accepting China's demands for an apology and retraction of her statement remains low. This is primarily because her hardline stance towards China and her consistent assertion that "a Taiwan contingency is a Japan contingency" continue to receive strong support from within the Liberal Democratic Party and conservative circles. Furthermore, public sentiment has soured due to China's retaliatory measures, leading to high approval ratings for the Такаichi cabinet, around 70%.

Prime Minister Такаichi's concern lies in the thawing U.S.-China relations. While the Trump administration's first term policies towards China aimed for victory in competition, employing a comprehensive offensive across trade, investment, values, and systems—including tariffs, investment restrictions, and criticism of human rights and the Communist Party's dictatorship—the second term, as previously described, has surprisingly shown competition and compromise confined to economic aspects. In April, the U.S. announced a de facto embargo, a 145% tariff on China, but retreated by postponing the tariff imposition for three months after China retaliated with export controls on rare earths. Ultimately, at the U.S.-China summit in Busan in October, Trump extended the tariff deferral by one year in exchange for China extending its export controls on rare earths and other key minerals for one year, and reduced the punitive tariff on fentanyl by 10%. With his political future tied to the November 2026 midterm elections, Trump is wary of Chinese economic retaliation and will continue to adopt a cooperative stance. Similarly, President Xi Jinping is expected to continue stabilizing U.S.-China relations to boost his country's sluggish economy. The two countries are likely to maintain a period of détente, especially with Trump's visit to Beijing scheduled for April. Against this backdrop, Trump reportedly advised Prime Minister Такаichi that it would be best not to provoke China over the Taiwan issue, and the White House stated that the U.S. must maintain a strong alliance with Japan while also preserving a good cooperative relationship with China.

The peculiar dynamic in 2026 is that Japan, the status quo power, and China, the power seeking to alter the status quo, are simultaneously engaging in friendly negotiations with the United States. Amidst the coexistence and intersection of U.S.-China relations seeking détente and Sino-Japanese relations in conflict, the Такаichi administration's dilemma will deepen. The détente in U.S.-China relations creates an incentive for Japan to choose Plan B due to distrust of the U.S., while the confrontation with China acts as an incentive to increase dependence on the U.S. The greater the military and economic threats and retaliation from China, the more Japan will have to rely on the U.S.-Japan alliance. In the short term, Sino-Japanese conflict is more likely to increase dependence on the U.S. for this reason.

V. Outlook for ROK-Japan Relations

For the Такаichi administration, which is grappling with establishing relations with the U.S. during a period of hegemonic readjustment and focusing its diplomatic efforts on improving relations with China, stabilizing ROK-Japan relations is essential. Prime Minister Такаichi, with her conservative leanings, has stated her intention to visit the Yasukuni Shrine at least once during her tenure. However, given the current diplomatic challenges, the likelihood of her undertaking a shrine visit that would provoke strong backlash from China and South Korea is low. Meanwhile, the Lee Jae-myung administration is managing ROK-Japan relations as a touchstone of pragmatic diplomacy, and shuttle diplomacy has been restored.

In South Korea's case, public opinion is also positive towards stabilizing ROK-Japan relations. A regression analysis of the ROK-Japan Public Perception Survey data, conducted annually since 2013 by the East Asia Institute (EAI) with its Japanese partner institutions (Genron NPO, 2013-2023; API, 2025), specifically focusing on the survey conducted from August 18-20, 2025, reveals that the significant independent variables influencing the improvement of ROK-Japan relations are impressions of the Japanese leader, impressions of Japan, and trust in the United States. The analysis indicates that the more favorable the impression of the Japanese Prime Minister, the more favorable the impression of Japan, and the higher the trust in the United States, the greater the perceived improvement in ROK-Japan relations (Sohn and Lee, mimeo).

Table 2. Analysis of Variables for ROK-Japan Relations Improvement (2025)

As shown in [Table 3], South Korea's favorability rating towards Japan has continuously increased from 12.3% in 2020 to 52.3% in 2025. During the same period, Japan's favorability rating towards South Korea rose from 25.4% in 2020 to 37.4% in 2023, then declined to 24.8% in 2025. The unfavorability rating increased from 46.3% to 51%. [Table 4]. The contrasting results in Japan can be partly attributed to the unfavorable impression of President Lee Jae-myung. 39.2% of Japanese respondents hold a negative impression of President Lee, with only 10.5% holding a positive impression [Table 5]. This can be seen as an extension of the negative image of past progressive administrations. Conversely, the positive impression of Prime Minister Ishiba among South Korean respondents surpassed the negative impression, standing at 32.5% [Table 6].

Since taking office, President Lee has emphasized pragmatic diplomacy and stated that overturning inter-state agreements, such as the comfort women agreement and the forced labor issue, is not desirable. He has even remarked that dwelling excessively on historical issues should not hinder cooperation. This indicates his intention to erase the anti-Japanese image formed during his time as an opposition leader. He has maintained friendly relations at the summit level, holding a total of five summit meetings since taking office, including three with Prime Minister Ishiba and two with Prime Minister Такаichi. It remains to be seen whether the impression of President Lee among the Japanese public will enter a phase of improvement. Similarly, the trend in the impression of Prime Minister Такаichi, who has a right-wing image, among the South Korean public is also noteworthy. How the public will react to Prime Minister Такаichi's efforts to convey a friendly image to the South Korean public is another point of interest.

Finally, there is the U.S. variable. The fact that increased trust in the U.S. correlates with a greater sense of improvement in ROK-Japan relations implies that higher trust in the alliance supports the improvement of ROK-Japan relations. Indeed, pressure from the U.S. (top-down) towards improving ROK-Japan relations has been consistently applied. Through the first Trump administration and the Biden administration, the U.S. has consistently pressured for improved ROK-Japan relations by establishing ROK-U.S.-Japan cooperation as a key means of its Indo-Pacific strategy to respond to regional challenges, provocations, and threats. As North Korea's nuclear-missile threats and China's challenges have increased, both South Korea and Japan have strengthened their security ties with the U.S. and consequently accepted U.S. pressure.

Will the U.S. factor continue to play a positive role in 2026? This is related to the degree of trust both South Korea and Japan place in the U.S. As shown in [Table 7], trust in the U.S. has significantly declined since 2022. Will this declining trend in trust continue? Will the decline in trust hinder ROK-Japan cooperation? Or will the two countries forge new cooperation as part of preparing Plan B? 2026 stands at a crossroads.

[Table 3] Impressions of the Other Country (2013-2025 South Korea)

[Table 4] Impressions of the Other Country (2013-2025 Japan)

[Table 5] Impressions of the Other Country's Leader (2014-2025 South Korea)

[Table 6] Impressions of the Other Country's Leader (2014-2025)

[Table 7] Trust in the Other Country (2017-2025 South Korea)

VI. Possibility of ROK-Japan Plan B Cooperation

The United States, the architect of the international order and its greatest burden-bearer, no longer exists in the same capacity, and Japan, the greatest beneficiary of that order, faces immense challenges. 2025 clearly demonstrated that relying on U.S. goodwill or optimistic projections about America's future—the prospect that the U.S. will recover the economic foundations of its hegemony and re-enter the normal track—is no longer viable. At the same time, it has also vividly shown that the U.S. remains an irreplaceable ally for Japan in terms of diplomacy, security, and economy. Therefore, Japan's future challenge is to view the U.S.-Japan alliance as a transaction and the U.S. as a tool, just as the U.S. views alliance relationships as transactions and alliance partners as tools. A shift in perspective, consciously adopting transactional, instrumental, and pragmatic realism in its relations with the U.S., is a prerequisite for exploring Plan B.

South Korea also needs a similar shift in perspective regarding its relationship with the U.S. This entails exploring a Korean-style Plan B. While ROK-Japan cooperation has progressed in recent years within the framework of ROK-U.S.-Japan cooperation under U.S. patronage, the time has come to explore ways for both countries to cooperate in mitigating U.S. risks. The time is ripe to initiate strategic communication towards 'ROK-Japan Plan B Cooperation,' including adjusting to appropriate levels of U.S.-ROK interdependence and establishing indispensable goods or chokepoints vis-à-vis the U.S. ■

References

Sohn, Yeol et al. 2025. "[EAI Public Opinion Briefing] Analysis of the Results of the 1st ROK-U.S.-Japan Public Perception Survey and the 12th ROK-Japan Public Perception Survey in 2025"https://www.eai.or.kr/press/press_01_view.php?no=13370

Sohn, Yeol. 2024. "[New Year's Special Commentary Series] ⑦ ROK-Japan Relations in 2024 Practicing the Spirit of Camp David: Challenges and Prospects." EAI Commentary. January 11.https://eai.or.kr/new/ko/pub/view.asp?intSeq=22299&board=kor_issuebriefing

Jeon, Jae-seong, 2026. "[New Year's Special Commentary Series] ② Changes in U.S. Foreign Policy and the International Order in 2026" https://www.eai.or.kr/press/press_01_view.php?no=13462

Akita, Hiroyuki, "The World Forced into Plan B: Reliance on 'Trump's America' Will Not Last" (November 7, 2024)https://www.nikkei.com/article/DGXZQOCD0694V0W4A101C2000000/

Ishii, Masafumi, "How Will Japan Respond to the U.S. National Security Strategy Based on Monroe Doctrine? An Interview with a Former Ministry of Foreign Affairs Official" (December 24, 2025)https://digital.asahi.com/member_scrapbook/detail.html?aid=ASTDR2S63TDRUTFK008M&cflag=0&psub=1&page=1&limit=20&sort=regtime.desc

Kojyo, Yoshiko et al., "The International Order Beyond 'U.S. Dependence' and Japanese Diplomacy," *Diplomacy*, vol 91, May/June 2025.

Sahashi, Ryo, "The World With the U.S.' and 'The World Without the U.S.'," *Chuo Koron*, December.

Mori, Satoshi, Yuichi Hosoya, and Michito Tsuruoka, "The World Buffeted by the Trump Administration," Global Trends #3 Foresight. (July 1, 2025)https://www.fsight.jp/articles/-/51468

Yul Sohn and Ahlim Lee, "Determinants of the Improved Japan-Korea Relationship." (mimeo)

■Sohn, YeolDistinguished Research Fellow, East Asia Institute; Professor, Graduate School of International Studies, Yonsei University.

■ Responsible and Edited by: Lee Sang-jun_EAI Research Fellow
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