Park Geun-hye’s historic impeachment as South Korea’s president, upheld by the Constitutional Court on Friday, has complicated Japan’s path to reconciling grievances between the two Asian giants — including on the “comfort women” issue — and could also impact their response to the escalating North Korean security threat.

While Prime Minister Shinzo Abe, in power since Park became president in 2013, has not seen eye to eye with her on every issue, together they made progress on one of the most intractable historical issues facing the two nations.

In December 2015, they reached an accord on dealing with the issue of comfort women, or those forced into Japanese military brothels before and during World War II. That accord promised to “finally and irreversibly” resolve the long-festering issue.

Abe and Park have also formed a united front in the face of North Korea’s ballistic missile and nuclear weapons development through cooperation with their common ally, the United States.

Abe has received support from voters for both initiatives, but may not have such a smooth ride with South Korea’s next leader.

Following Park’s impeachment by the court, confirming a vote by the National Assembly over a corruption and abuse-of-power scandal, a presidential by-election must be held in the next 60 days.

“The presidential election will take place in an advantageous environment for the opposition parties,” said Masao Okonogi, professor emeritus at Keio University in Tokyo.

Moon Jae-in, of the main opposition Democratic Party, is the leading candidate, with a support rate of more than 30 percent among voters, according to polling. He has called for a renegotiation of the comfort women accord.

Aside from Moon, Ahn Cheol-soo, leader of the minor opposition People’s Party, and other contenders have said they want the deal reviewed.

While Park promoted the agreement, the last few months of her term saw bilateral tensions spike over the issue.

Yasumasa Nagamine, Japan’s ambassador to South Korea, has yet to return to Seoul after being recalled Jan. 9 to protest the installation by civic groups in December of a statue commemorating comfort women in front of the Japanese Consulate in Busan.

The statue is of the same design as one in erected front of the Japanese Embassy in Seoul and in several locations overseas. The latest statue went up in Germany on Wednesday.

The Japanese government has repeatedly called for South Korea to “steadily implement” the 2015 agreement, including by “resolving” the issue of the statues — which to Tokyo means removing them.

This is likely to be a hard sell for any prospective South Korean leader, particularly in light of the need to unite a public stirred up by the Park debacle. Three people died and dozens were injured in demonstrations in streets of Seoul near the court Friday.

A show of resilience toward Japan over historical and territorial grievances may be a safe issue to unite a divided voting base.

But over time, the need to keep relations with Japan intact for strategic reasons could see Moon or another successor change his tune on the issue, Okonogi said.

“Right now, those expected to be put up as candidates from the opposition parties are expressing negativity about the (comfort women deal), but if elected, they must persuade the public to keep the promise made with Japan,” he said.

A source close to Moon said it will not be easy to overturn the agreement, hinting that Moon may alter his stance to take a more pragmatic path on the deal if he becomes president.

For Japan’s part, Nagamine “had better return to his post soon in anticipation of dialogue with the new administration,” Okonogi said.

After news of the impeachment broke Friday, Japanese government officials stuck to their line that the government will “consider the various factors” before making a decision on when to return Nagamine to Seoul.

Abe and Park’s successor will also have to tackle the shared threat from North Korea, which this week fired four ballistic missiles nearly simultaneously into waters near Japan.

Moon has expressed reservations about the planned deployment of an advanced U.S. missile-defense system known as the Terminal High Altitude Area Defense system (THAAD), a decision made by Park.

He has also questioned the Park administration’s signing with Japan in November of a military intelligence-sharing pact called the General Security of Military Information Agreement (GSOMIA).

Fukushiro Nukaga, head of a cross-party Japan-South Korea parliamentarians’ league in the Diet, expressed concern about the potential for an “excessive reaction” by the next government in its stance toward Japan.

U.S. President Donald Trump, meanwhile, could end up uniting the leaders in certain respects. He has vowed to take firm action on Pyongyang, a push certain to require the coordination of Japan and South Korea.

With such a range of issues at play, the Abe administration’s success in reaching out to the next South Korean president may be measured by how soon Japan can set up the next trilateral leaders’ meeting with China.

It was Japan’s turn to host the summit before the end of last year, but planning was derailed by anti-Park protests and the impeachment vote against her.

Kyodo