Japan–Republic of Korea Ties Post Yoon Suk-Yeol’s Ouster

Introduction

The Republic of Korea’s (hereafter referred to as the ROK) Constitutional Court on 3 April 2025 upheld the impeachment of former president Yoon Suk-Yeol on charges of attempting to subvert the ROK’s Constitution by enacting an ill-advised autogolpe. Prime Minister Shigeru Ishiba, attending the Diet’s crucial Budget Session, was questioned by lawmakers as to Japan’s next steps. Ishiba’s short response[1] emphasised the importance of cooperation with the ROK and faith in the democratic process to elect new leaders whom his administration would happily engage in talks.

Ishiba’s response may have satisfied speculations for now, but it also highlighted the lack of any desirable options for Japan. As a new constellation of political forces emerges in Seoul, and as the US engages in a trade war by imposing tariffs on allies and rivals alike, ties with the ROK have attained critical importance for Tokyo.

Japan–ROK Ties Before and After Yoon’s Election

Yoon’s election in 2021 was opportune for the Japanese, as his predecessor, Moon Jae-in, presided over the worst crisis in Japan–ROK ties since the normalisation of relations in 1965. The genesis of this crisis lay in the ROK Supreme Court in 2018 issuing a verdict granting substantial monetary compensation to two Koreans who had accused Mitsubishi Heavy Industries of coercing them into working in hazardous conditions during the late colonial period.[2] The Supreme Court judgement resulted in placing the government of the ROK directly in the line of sight of then-Prime Minister Shinzo Abe.

Abe first tried to pressure the Moon administration to ignore the judgement, only to be told that Seoul was firmly behind it.[3] The subsequent acrimony lasted almost five years, with key high-technology exports held hostage,[4] critical military information exchange halted with the ROK’s suspension of the General Security Of Military Information Agreement (GSOMIA)  with Japan in August 2019,[5] and public opinion cratering on both sides of the Sea of Japan.[6]

The situation was ameliorated somewhat when Yoon was elected.[7] On the other hand, Tokyo saw the emergence of former Foreign Affairs Minister Fumio Kishida on the national stage as the nation’s new Prime Minister in late 2021.[8] Known to be pragmatic and middle-of-the-road when it came to bilateral issues, Kishida and Yoon immediately set about improving ties. They met a dozen times over the two years in which their tenures overlapped (2022–2024). A signal achievement of these meetings was a ‘forward-oriented’ Japan–ROK relationship, which relegated historical issues to the back burner in order to focus on the clear and present challenge posed by China as well as the Democratic People’s Republic of Korea (whose missile capabilities were growing by the day).[9]

Taking a cue from the breakthrough, President Joe Biden invited both Yoon and Kishida to Washington.[10] Then, in August 2023, the three leaders met at the US presidential retreat of Camp David, where they came up with the Camp David Declaration institutionalising trilateral cooperation against regional and global challenges.[11] Yoon and Kishida’s working relationship formed the foundation on which these new structures could be built.

December Coup and Japanese Policy Thinking

The night of 3/4 December 2024 raised question marks about the fate of this progress. Yoon’s brief declaration of martial law, followed by the despatch of military forces to the National Assembly, met with potent opposition from legislators. The latter immediately voted to nullify the relevant declarations and return the military to its barracks, halting his self-coup in its tracks. He was forced to step down and went into hiding for some time before finally surrendering to the authorities.[12]

The speculation on the reasons for Yoon’s actions are immaterial here.[13] What is certain, however, is that Japan has lost its most reliable interlocutor. As such, its alarm at the events unfolding in Seoul cannot be characterised entirely as an expression of pious concern about a neighbouring democracy. They betray a rather profound sense of dismay about the possible undoing of the progress made in recent years.

Since the events of 3/4 December, the Japanese have engaged their ROK counterparts at all levels, with Foreign Affairs Minister Takeshi Iwaya and his Korean counterpart Cho Tae-yul emerging as key nodes. A running thread throughout all these discussions is a concern for the possible snapping of key strategic communication lines running between the two capitals, indicating clearly a desire in Tokyo to avoid a rehash of the Abe-Moon spat.[14]

For its part, Seoul has sought to reassure Tokyo  that bilateral dialogue mechanisms remain intact and that the ROK continues to repose strategic trust at both bilateral and trilateral levels. How far these assurances reassure Tokyo is a different matter, as it is all too aware that a change in government would bring new interlocutors with different motives to the fore.

Need for Japan–ROK Ties

Japan’s anxiety is not unfounded. Japan–ROK ties have gained importance not only in the security domain, but also increasingly in the economic domain. The latter facet has become especially relevant after 4 April 2025, when President Donald Trump announced steep ‘retaliatory’ tariffs which he labelled as ‘Liberation Day’.[15] Japan was charged 24 per cent under the Trump Tariffs, while the ROK was charged 25 per cent. Though the Trump Administration subsequently backed down, a permanent solution to such actions by the US in future requires joint action, especially in light of Trump’s long-standing grievances regarding US manufacturers’ purported lack of unfettered access to international markets.

Another critical factor requiring good ties with the ROK is Japan’s growing rapprochement with the other superpower, China. The recently concluded Trilateral Foreign Ministers’ Meeting[16] (as well as the subsequent Economic and Trade Ministers’ Meeting) may have been partly a response to Trump’s threatened tariffs, but the timing of the meeting (several days before Trump’s announcement) as well as the contents of the issues discussed do not indicate that to be the sole cause.

In fact, it may plausibly be argued that the trilateral was part of a strategy by Tokyo (and possibly Seoul) to create a fall back that fireproofs their economies against Trump’s autarkic reflexes, while at the same time maintaining a suitable distance between themselves and Beijing so as to prevent easy co-optation. The official transcripts of the meeting issued by the Ministry of Foreign Affairs in Tokyo indicate that security-driven factors have played a big role as well. The Japanese seem to be as concerned about re-establishing confidence-building measures with Beijing as with economic integration. Undoubtedly, the recent escalation of tensions around the disputed Senkaku/Diaoyu Islands is relevant here,[17] as is the spate of attacks, possibly motivated by xenophobia, on Japanese citizens residing in China.

Seen in this light, the trilateral can be interpreted as an attempt by Japan, in association with the ROK (which shares many of Japan’s security concerns with regard to China), to balance China. By creating a one-stop-shop where the two countries may communicate with its bigger neighbour, while attempting to read its next moves, Japan may also simultaneously be expressing a desire to retain enough strategic autonomy to lean ever-so-subtly towards Beijing, should actions by Washington be perceived as sufficiently threatening to its interests.

No matter the impelling factor, it is unquestionably imperative for Japan and the ROK to work together, especially given the ever-present risk that Beijing may try to co-opt the trilateral to suit its own ends, or that the US may choose to take an aggressive stance vis-à-vis its allies in the Indo-Pacific as it has threatened to do in the Euro-Atlantic. If the ROK, under a future leader seeking to align with China against Japan, chooses to scuttle the latter and proceed with negotiations with Beijing bilaterally, the prospects of regional economic and security coordination will be lost for at least a decade, if not more. Moreover, strategic trust and cooperation between the two countries is sure to erode significantly.

Conclusion

As preparations for a new general election get underway in the ROK, polls indicate that Democratic Party of Korea head Lee Jae-Myung is most likely to become President. Lee is a point of particular concern in Tokyo, as his public statements betray an unprecedented degree of vitriol against them. In 2022, after US–Japan–ROK drills were conducted in the Sea of Japan, he claimed that the ‘Japanese military’ would ‘invade the Korean peninsula and hang the Rising Sun flag again’. He also claimed that the exercises were ‘an act recognising the Japanese Self-Defence Forces as an official army’.[18] In a subsequent incident, he referred to Japan as a ‘militarily hostile state’ and the Yoon-Kishida summit as a ‘surrender ceremony pleading for reconciliation’.[19] Though he seems to have subsequently reversed some of his positions, espousing deeper trilateral cooperation and expressing ‘deep affection’ for Japan in a meeting with the Japanese ambassador to Seoul,[20] it is too early to see whether he would opt to lend substance to the former group of statements or the latter.

In the meantime, Japan is left with no good options. It can no longer rely on the US for assistance in keeping the ROK committed to trilateral cooperation, as it is not even clear whether President Trump’s interest in the Indo-Pacific is normative or merely transactional.[21] At present, it has no viable options to influence any possible outcome, and can only wait, watch and hope that Yoon’s successor sees value in continuing to work with Tokyo for a future-oriented partnership.

Views expressed are of the author and do not necessarily reflect the views of the Manohar Parrikar IDSA or of the Government of India.

[1] “石破首相「日韓連携は重要」(Prime Minister Ishiba: Japan-Korea Cooperation is Important)”, Jiji.com, 4 April 2025.

[2] Chiharu Shibue, “2nd Top S. Korean Court Ruling Orders Mitsubishi Heavy to Compensate Ex-forced Laborers”, Mainichi Shimbun, 29 November 2018.

[3] Tim Kelly and Hyonhee Shin, “South Korea Risks Ties by Disbanding ‘Comfort Women’ Fund – Japan PM”, Reuters, 21 November 2018.

[4] Ulv Hanssen, Eun Hee Woo, Petter Lindgren and Wrenn Yennie Lindgren, “The Identity Politics Driving the Japan-South Korea Trade War”, Commentary, East Asia Forum, 25 November 2019.

[5] Takuya Suzuki and Kiyohiko Inada, “S. Korea Notifies Japan of ‘Normalization’ of GSOMIA Pact”, The Asahi Shimbun, 22 March 2023.

[6] “The Japan-South Korea Joint Public Opinion Poll 2019”, Public Opinion Research Institute Corporation & Hankook Research Co. Ltd, 12 June 2019.

[7] Koh Ewe and Jake Kwon, “Who is Yoon Suk Yeol, South Korea’s Impeached President?”, BBC, 3 April 2025.

[8] Craig Mark, “Who is Fumio Kishida, Japan’s New Prime Minister?”, The Conversation, 29 September 2021.

[9] Ryo Hinata-Yamaguchi, “What to Expect from Japan-South Korea Relations After Kishida”, The Atlantic Council, 6 September 2024.

[10]           “Readout of President Biden’s Meeting with President Yoon Suk Yeol of the Republic of Korea”, The White House, 18 August 2023; “日米首脳会議 (Japan-U.S. Summit Meeting)”, Public Relations Office, Government of Japan, 13 January 2023.

[11]           “日米韓共同記者会見 (Japan-US-ROK Joint Press Conference)”, 首相官邸 (Prime Minister’s Office of Japan), 18 August 2023.

[12]           Vina Nadjibulla and Erin Williams, “Explainer: Democracy Under Pressure: Yoon’s Failed Martial Law and South Korea’s Political Turmoil”, Asia Pacific Foundation of Canada, 10 December 2024.

[13]           Ibid.; also see Koh Ewe and Jake Kwon, “Who is Yoon Suk Yeol, South Korea’s Impeached President?”, no. 7.

[14]           “Japan-ROK Foreign Ministers’ Telephone Talks”, Ministry of Foreign Affairs of Japan, 23 December 2024; “Japan-ROK Foreign Ministers’ Meeting”, Ministry of Foreign Affairs of Japan, 13 January 2025; “Japan-ROK Foreign Ministers’ Meeting”, Ministry of Foreign Affairs of Japan, 22 March 2025.

[15]           Mark John, “Trump’s Tariff Formula Confounds the World, Punishes the Poor”, Reuters, 4 April 2025.

[16]           “The Eleventh Japan-China-ROK Trilateral Foreign Ministers’ Meeting”, Ministry of Foreign Affairs of Japan, 22 March 2025.

[17]           “Chinese Ships Stay in Japanese Territorial Waters for Record Time; Break Previous Record of Roughly 80 Hours”, The Japan News By The Yomiuri Shimbun, 24 March 2025.

[18]           Sarah Kim, “DP Chief’s Warning about Japan Sets Off Political Firestorm”, Korea JoongAng Daily, 11 October 2022.

[19]           Choo Jae-woo, “Is Lee Jae-myung’s Diplomatic Shift an Attempt at Redemption?”, The Korea Times, 13 February 2025.

[20]           Ibid.

[21]           Liam Gammon, “Trump White-Ants US Democracy and Opens a Values Gap with Allies”, Commentary, East Asia Forum, 6 April 2025.