The Republic of Korea is set to have a presidential election, likely in early May, thanks to the country's Constitutional Court stripping Park Geun-hye of her presidential powers on Friday.

Many parts of the world - the ROK's neighbors and allies in particular - are watching closely what will happen next. Among them, Japan has the reason to worry about relations with its neighbor.

The main presidential candidates in the ROK have committed themselves to repeal, or at least renegotiate, the agreement on the issue of Japan's wartime sexual slavery of Korean women, known euphemistically as "comfort women", which was inked between the ROK and Japan on Dec 28, 2015.

According to the deal, Japan offered an apology and one billion yen (approximately $8.7 million) to establish a fund that offers payments to the surviving comfort women and their families. In exchange, the ROK is supposed to let the issue rest, with the two governments pledging to refrain from criticizing each other regarding comfort woman issues in international settings including the United Nations. The ROK also agreed to strive to resolve the issue of the statue of a comfort woman located in front of the Japanese embassy in Seoul.

A Gallup Korea poll released on Friday showed that the former Democratic Party leader, Moon Jae-in, currently leads the prospective field of ROK presidential candidates with a 32 percent approval rating. Ahn Hee-jung, governor of South Chungcheong Province, is in second place with a 17 percent approval rating.

Moon Jae-in has described the Dec 28 agreement as "a good example of deep-rooted problems with our foreign policy", adding that what Japan needs to do is to acknowledge its legal responsibility and to make an official apology. "We need new negotiations that will make this clear," Moon has said.

The 2015 settlement, which both the ROK and Japan agreed to end the issue of the comfort women "fully and irreversibly", seems on the brink of falling apart.

Critics in the media and civil society in the ROK described the deal as Park effectively selling out the dignity of survivors of wartime sexual slavery for short-term diplomatic and geopolitical gain.

Some have called on their government to return the compensation back to Japan. And some of the surviving comfort women and their supporters in the ROK have denounced the apology as informal and insufficient, and they have rejected the informal donation and instead call for formal compensation.

A new comfort women statue was installed in front of the Japanese consulate in Busan in December. In early January, Japan recalled its ambassador to the ROK, Yasumasa Nagamine, in protest. Yasuhiro Morimoto, Japan's consul general in Busan, was also recalled "temporarily". Japan has also halted negotiations on currency swaps between the Korean won and the Japanese yen.

The future of the General Security of Military Information Agreement the two countries signed in November is also uncertain, as the agreement is criticized by opposition parties in the ROK.

The absence of a Japanese ambassador in Seoul highlights how fragile the relationship between the two East Asian nations is.

The ROK and Japan failed to resolve their diplomatic frictions at the G20 foreign ministers' meeting in Bonn on Feb 17. ROK Foreign Minister Yun Byung-se and his Japanese counterpart Fumio Kishida discussed the issue of the comfort woman statue in Busan, but could not bridge the two countries' differences.

The United States wants its East Asian allies to establish close cooperation. But the prospects for closer ROK-Japan cooperation are not promising. Moon Jae-in says the deployment of the Terminal High Altitude Area Defense anti-missile system in his country should be reviewed.

The author is China Daily Tokyo bureau chief. caihong@chinadaily.com.cn