On March 16, South Korean President Yoon Suk-yeol made his first official trip to Tokyo, where he met Japanese Prime Minister Fumio Kishida. It was the first summit between leaders of the two countries in more than a decade, marking the culmination of a diplomatic revival that began on the fringes of the United Nations General Assembly last autumn.

The meeting was hailed by both sides as a success. Yoon said it resulted in “fruitful discussions that can transform Korea-Japan relations, which have been at a standstill, into a relationship of cooperation and mutually beneficial development.” Kishida called it a “major step toward normalizing relations.” Concretely, the summit resulted in Japan and South Korea easing trade controls, committing to frequent reciprocal visits, and maybe most importantly, reviving the 2016 General Security of Military Information Agreement (GSOMIA), a key plank in coordination with the United States on intelligence matters that Seoul all but suspended in 2019. It also gave a major nod toward Washington, which has expressed concern over the fraught bilateral relations at a time when it is focused on sprucing up its alliances to counter China’s growing influence in the region.

The credit for the dramatic diplomatic reversal largely goes to Yoon, who since taking power last year has made it his business to restore friendly relations with Tokyo. Until then, Japan’s stance toward South Korea had been one of frustrated indifference ever since the late-2017 collapse of a 2015 agreement compensating Korean women coerced into sexual labor during World War II. The administration of Yoon’s predecessor, Moon Jae-in, saw the deal as illegitimate and used the impeachment of the president who negotiated it, Park Geun-hye, as an effective basis for its abrogation.

The relationship steadily deteriorated throughout the rest of Moon’s tenure. In November 2018, Korean courts ordered two Japanese firms, Nippon Steel Corporation and Mitsubishi Heavy Industries, to pay compensation to South Koreans forced to work in their factories during the late colonial period, from around 1939 to 1945. The following month, a Korean naval destroyer directed its fire-control radar at a patrol aircraft from Japan’s Maritime Self-Defense Force conducting surveillance activities in the East Sea/Sea of Japan. In a tit-for-tat move in the autumn of 2019, the two countries removed one another from their trade whitelists, and soon after, South Korea unilaterally sought to suspend the GSOMIA agreement. Whilst Seoul did not carry out this last threat in full, political and military relations were brought to a near-complete standstill.

But while the Tokyo summit finally brings the curtain down on an extended and troubling period of bilateral friction, enormous challenges remain on the path to achieving what both governments seek: maximizing mutual economic benefits whilst minimizing instability in Northeast Asia. Widespread contempt within South Korea for Yoon’s outreach is proving to be a particular stumbling block. Some Koreans still have—and a great many more are socialized into—painful memories of the violence unleashed during Japan’s colonial occupation, and resent what they see as a lingering Japanese tendency to glorify it. In a recent poll by Gallup Korea, 64 percent of respondents said there need not be any effort to improve ties if Japan’s attitude did not change.

In this context, Yoon’s that Korean companies that benefited from wartime reparations in the 1960s would compensate the victims of Japanese forced labor, rather than the Japanese firms themselves, was greeted with anger. Many South Koreans consider the move to be an act of unilateral capitulation, and a betrayal.

The bilateral relationship is also hostage to political opportunism in South Korea. Back at the outset of Yoon’s journey to restore relations, opposition leader Lee Jae-myung voiced the fanciful idea that a trilateral naval drill with Japan and the United States could presage Japanese boots on the ground in Korea, an idea that colonial history makes completely untenable. True to form, Lee’s response to last month’s summit was to accuse Yoon of selling out “our country’s pride, the victims’ human rights, and the justice of history, all of that, in exchange for a bowl of omurice,” referring to an omelet dish that Yoon is fond of, and which the Japanese provided during the summit visit.

This is all somewhat regrettable, for whilst largely understandable, South Korean public opposition to warmer ties with Japan under present circumstances is unhelpful for regional stability. Now more than at any time in recent memory, regional geopolitics call for greater coordination between these large East Asian democracies, significantly integrated economies, and key American allies, particularly in facing up to China in the post-Ukraine world.

Whatever happens domestically in the South, both Seoul and Tokyo must tread carefully as they restore relations if they do not want to further disturb the wider region, even unintentionally. That other regional concern, North Korea perceives the ongoing rapprochement between the two as engineered by Washington, which it also suspects of pushing for a return to scaled-up military exercises in South Korea this month, and of encouraging Tokyo to ramp up its defense capabilities. Japan late last year that it plans to double its defense budget to 2 percent of GDP by 2027 and is now developing counterstrike capabilities for the first time.

For Pyongyang, the logical conclusion is that it must enhance its own capabilities to counter the United States “zealously egging the puppets [South Korea] and Japan on to dangerous arms buildup under the signboard of implementing the ‘Indo-Pacific strategy’ aimed at maintaining regional military strategic hegemony,” as state media put it in a key commentary on March 17. Leader Kim Jong Un announced in his speech to a party meeting at the turn of the year that North Korea would expand its nuclear arsenal to do exactly that.

The supercharged regional arms race that could result from these dynamics would be detrimental to U.S., Japanese, and South Korean interests alike. In South Korean public opinion, there is already fear that a closer trilateral relationship between the three allies could spur an ever-closer relationship between China, North Korea, and Russia. Even if such a scenario is unlikely—Pyongyang’s deep paranoia means it’s unlikely to cooperate closely with anyone, even an ally like China—the risk remains that the Japan-South Korea rapprochement will add fuel to the fire of Pyongyang’s militarism.

There is every reason for Japan, South Korea, and the United States to cooperate in maintaining peace and stability in East Asia, and normalization of the GSOMIA agreement is a particularly welcome step in that direction. But discretion is also the better part of valor, and all three parties should proceed without excessive fanfare if they want to avoid bringing about more of the kind of instability that the flawed Japan-South Korea rapprochement is partly intended to preempt. Big joint military exercises that the U.S. and Korean armies conducted in March probably should have been executed with fewer journalists in attendance. And it is cause for concern that even bigger live-fire exercises are scheduled for the 70th anniversary of the U.S.-South Korea alliance in June, raising the prospect of a still more bellicose North Korean response.

The opinions expressed are the author’s own and do not represent any institution with which he is affiliated.