Japan, South Korea Put New Value on Mutual Ties as Trump, China Shake Up World Order

By Satoshi Ogawa

8:00 JST, April 4, 2026

The world order that the United States has taken charge of, and that Japan has taken advantage of, is fading away under the Trump 2.0 administration and the growing hegemonic threat from China. This means that Japan faces the need to reshape its foreign and security policy, which strongly relies on the United States as its only ally. There is a certain other country facing the same national security and foreign policy challenges. It’s South Korea. Against this backdrop, the relationship between Japan and South Korea, which has been hindered by historical conflict, is at a critical strategic turning point.

“In the current strategic environment, in which the importance of Japan-ROK relations is growing, we will work to further strengthen our relationship through candid exchanges of views based on the relationship of trust between President Lee [Jae Myung] and me.” Prime Minister Sanae Takaichi explained her administration’s South Korea policy in this way in her first policy speech at the ordinary Diet session on Feb. 20.

Before she took office, it was believed that she would surely make the relationship worse if she were to become prime minister. In fact, in the Liberal Democratic Party’s presidential election in September 2024, then Prime Minister Fumio Kishida ordered his faction members to vote against her because he was concerned that the Japan-South Korea relationship that he had worked to improve would be critically worsened by her hawkish and ideological foreign policy stance, especially her pledge to worship at Yasukuni Shrine. That was the main cause of her loss in the final vote.

But she has taken a more practical foreign policy stance as prime minister, especially toward South Korea. Soon after taking office in October 2025, she visited South Korea to participate in the Asia-Pacific Economic Cooperation (APEC) summit there, and while in the country she also met with Lee. At their first meeting she stressed that she would strengthen ties in a future-oriented manner and boost cooperation in their mutual strategic interest.

Her stance was well received in South Korea. Lee praised her, saying, “All my worries are gone.” In a mirror image, Lee himself was a politician whom many in Japan had worried would worsen the Japan-South Korea relationship through his anti-Japan sentiment if he were to become president, but in reality he changed his foreign policy stance in a practical way once he took office.

These two leaders’ changes of mind occurred not only because of their political maneuvering but also because of strategic decisions by both countries.

It had been believed by conservatives in Japan that South Korea put more importance on its relationship with China than on its relationship with Japan. According to the results of a public opinion survey conducted by the Japan Press Research Institute (JPRI) in fiscal 2016, only 32.3% of South Koreans had favorable views of Japan, while the number of those with favorable views of China was far higher at 55.6%.

South Korea apparently hoped China would be able to stop North Korea from its provocative behaviors, such as developing nuclear weapons, and that South Korea could thrive if it strengthened economic ties with China. On top of that, some experts including Edward Luttwak, a historian and worldwide authority on strategic relations, pointed out that South Korea had a deep cultural respect for China and the Chinese.

Contrary to South Korea’s expectations, North Korea has not listened to China and has continued its military buildup, including nuclear weapons. Also, China hasn’t brought prosperity to South Korea, but rather has weaponized economic relations when it thinks South Korea is doing something against China’s will, such as deployment of the advanced missile defense system called THAAD in 2017. China retaliated against South Korea by canceling group tours to the country and organizing a boycott of Korean supermarkets and products in China.

The JPRI surveys showed how South Koreans soured on China after those unfriendly behaviors. In the FY2017 survey, South Koreans with favorable views toward China dropped 8.5 points from FY2016 to 36.5%, then in FY2018 dropped further to 28.6%. In short, China’s reaction to the THAAD deployment made South Koreans realize they could not and should not count on China.

A source of worry from another direction was the “America First” foreign and security policy of U.S. President Donald Trump, who repeatedly complained that South Korea had been free-riding on the U.S. forces there for defense. In fact, the first Trump administration is said to have considered withdrawing a significant portion of U.S. forces from South Korea. It also threatened to scrap the U.S.-Korea Free Trade Agreement. The second Trump administration has pressed the country to drastically increase its defense burden-sharing and its investment in the United States.

In light of the strategic challenges posed by China and the United States, South Korea was forced to reconsider its relationship with Japan. Even so, South Koreans’ favorability toward Japan continued to stay around 30% until FY2021, according to JPRI surveys. Conflicts over historical issues, such as those of former wartime comfort women and former wartime requisitioned workers, remained a major obstacle to improving the relationship.

However, when Yoon Suk Yeol took office as South Korea’s president in May 2022, he finally decided to let it go and move on. In a March 2023 interview with The Yomiuri Shimbun, Yoon pledged that those issues would never flare up again. In fact, he broke the cycle of Korean leaders politicizing those issues. South Koreans’ favorability toward Japan in the JPRI survey increased to 39.9% in FY2022 and to 44.0% in FY2023. As current President Lee has maintained Yoon’s stance, South Koreans’ favorability toward Japan increased in the FY2025 survey to 56.4%, exceeding 50% for the first time since the survey was first held in FY2014.

From Japan’s point of view, South Korea has been a like-minded country but an undependable one, because the country was periodically overwhelmed by anti-Japanese sentiment and repeatedly reneged on agreements, especially regarding historical issues. The consistent Japan policy of both conservative Yoon and left-leaning Lee and the recent trend of growing South Korean favorability toward Japan can change such a cold view.

As I mentioned, Japan is faced with a need to reshape its foreign and security policy, which strongly relies on the United States as its only ally. The only available option is to strengthen ties with like-minded countries — and the Takaichi administration seems to think one of the most important like-minded countries could be South Korea.

In a symbolic event, Takaichi’s new recognition of South Korea was shown when she invited Lee to her hometown of Nara City and then played a drum session together with him this January. Who would have thought conservative Takaichi and left-leaning Lee would ever give a drum performance together?

The two leaders could, and might, shape a new era of Japan-South Korea relations in which both counties elevate the relationship to a strategic partnership or “quasi-alliance.”

To do so, Takaichi and Lee will have to make further efforts to deepen cooperation in areas that serve our mutual national interests, such as defense, trade and investment, economic security, and cultural and human exchanges.

Political Pulse appears every Saturday.

Satoshi Ogawa

Satoshi Ogawa is the deputy chief of the President’s Office of The Yomiuri Shimbun.