► On the sidelines of the G7 Summit, President Yoon and Prime Minister Kishida met for the third time and demonstrated the “deep trust” between them. That progress is due in large part to Yoon’s willingness to take politically risky, but geostrategically critical, decisions that have measurably improved the Korea-Japan bilateral relationship in just a number of months.

► Three areas are ripe for cooperation: preventing economic coercion, coordinating on extended deterrence, and building resilient regional institutions.

After a joint visit to the memorial for Korean victims at the Hiroshima Peace Memorial Park, President Yoon Suk Yeol called Prime Minister Kishida Fumio’s decision to join him a “brave act.” That is undoubtedly correct, but the same is true of Yoon’s own engagement with Kishida this year. On the sidelines of the G7 Summit, President Yoon and Prime Minister Kishida met for the third time and demonstrated the “deep trust” between them. That progress is due in large part to Yoon’s willingness to take politically risky, but geostrategically critical, decisions that have measurably improved the Korea-Japan bilateral relationship in just a number of months.

As a result, Seoul and Tokyo are opening a new chapter in their bilateral relationship. And along with U.S. President Joe Biden, President Yoon and Prime Minister Kishida could usher in a new era of trilateral cooperation between the United States, South Korea, and Japan. Prime Minister Kishida’s decision to invite President Yoon to the G7 Summit allowed the three leaders to meet briefly. Although it is unfortunate that President Biden chose to cut short his Asia trip after only a trilateral photo opportunity, the leaders will have other opportunities to meet at the Asia Pacific Economic Cooperation Summit and the East Asia Summit later this year.

The United States is one of the factors driving South Korea and Japan closer together, but not in the way one might expect. Of course, Seoul and Tokyo are both allies of Washington. Yet previous U.S. efforts to improve bilateral ties have failed despite robust U.S. support. One factor that is different this time is that neither Korea nor Japan can be completely confident in the direction that the United States will take in the years ahead. It is therefore incumbent that both countries work together to keep the United States present and active in the Indo-Pacific region while hedging against the unlikely but not unthinkable possibility of U.S. disengagement.

The other major difference from the last serious attempt to improve bilateral ties in 2016 is that both South Korea and Japan have more reason than ever to worry about North Korea, China, and even Russia. For many years, Pyongyang’s belligerence was the main factor driving Seoul and Tokyo together. But now both countries are confronted by growing pressure from Beijing and shocking recklessness from Moscow. All three of those autocratic governments are now engaged in rapid nuclear build ups, irresponsible nuclear signaling, or both. This has driven the need for greater cooperation between South Korea, Japan, and the United States.

Bilateral and trilateral cooperation are not a panacea – improved ties will not on their own solve these mounting threats. But South Korean and Japanese regional and global interests have never been more similar. President Yoon’s shift away from a narrow focus on the Korean Peninsula and toward the role of a “global pivotal state” requires that Seoul adjust its geostrategic horizons. Japan has already sought to do so with its more “proactive” regional and global approach. As a result, Tokyo can be a valued partner in lending Seoul a helping hand in these efforts. So while both countries will benefit from the improvement in their bilateral relationship, South Korea arguably has more to gain at the moment.

One reason that Japan can be so helpful to South Korea is that Tokyo is already integrated into some key global and regional groups, such as the G7, the Quadrilateral Security Dialogue, and the Comprehensive and Progressive Agreement on Trans-Pacific Partnership. To date, South Korea has been on the outside looking in at these groups, either unwilling or unable to join. Full Korean membership in the G7 or Quad may be unlikely, at least for the time being, but closer cooperation with these groups would be deeply beneficial for Seoul. This helps to explain why it is so important that Tokyo is now inviting the Korean president to join the G7 Summit as an observer – it is a step toward President Yoon’s objective of being a more pivotal global player.

Maintaining bilateral and trilateral momentum will be critical if South Korea and Japan are to avoid backsliding. After years of failed efforts to address their differences, it is remarkable how fast these ties have advanced. But as students of Korea-Japan relations know all too well, progress today does not imply continued improvement tomorrow. There are numerous domestic and historical issues that could create problems for the two governments. The only thing that can prevent these challenges from derailing the bilateral relationship is a genuine willingness by both leaders to make real progress and demonstrate tangible results.

So what should be next on the agenda? Three areas are ripe for cooperation: preventing economic coercion, coordinating on extended deterrence, and building resilient regional institutions. All three call for deeper bilateral and trilateral cooperation.

First up should be economic cooperation to address the challenge of economic coercion. South Korea and Japan have both faced economic pressure from China over the last decade, so each has an interest in avoiding over-reliance that could provide Beijing undue coercive leverage. As Korean and Japanese business navigate these challenges, they will be in a stronger position if both countries can align their policies with each other and with the United States. As three of the world’s leading technology innovators, they should align technology policies on everything from supply chain security to industrial policy to export controls.

Second on the list should be extended deterrence coordination. South Korean concerns about the nuclear postures of North Korea, China, and Russia—along with fears about American unreliability—have forced a new set of conversations about extended deterrence. It is only natural that Japan has similar questions, which may have to be addressed with its own Washington Declaration. Conducting extended deterrence discussions trilaterally (or even quadrilaterally with Australia) is logical, since any change in U.S. nuclear posture in Northeast Asia will impact both Seoul and Tokyo.

Third and finally, South Korea and Japan have an opportunity to build more resilient regional institutions. This will require groupings that are resilient both to the likelihood of Chinese pressure as well as the possibility of U.S. disengagement or distraction. For decades, Asia’s security architecture has been built around a hub and spokes model, with Washington as the hub, and Seoul, Tokyo, and others as separate spokes. Connecting these spokes, and making them hubs in their own right, is now vital. Doing so can both make it harder for countries like China to reject regional institutions, rules, and norms as vestiges of a U.S.-created system. It can also insulate regional states by increasing resilience in the case of a less engaged United States.

These steps will take time, and they will not be easy. But the fact remains that this sort of sustained bilateral and trilateral engagement would have been nearly impossible to imagine even one year ago. Leaders in South Korea, Japan, and the United States should be proud of what they have accomplished. But the challenge for Seoul, Tokyo, and Washington is to look forward, not backward, so now it is time to demonstrate that this improved atmosphere can lead to tangible benefits for all three countries.