Japan and South Korea struck a landmark agreement last month to "finally and irreversibly" resolve the "comfort women" issue - that of Korean women forced into wartime Japanese brothels. The accord paves the way for the two neighbours to put history behind them and move their relationship forward in the face of an increasingly assertive China and a nuclear-armed North Korea.

Japanese experts have hailed the Dec 28 breakthrough in the decades-long impasse, saying the deal is well calibrated so it can satisfy the public in both countries without undermining their official positions.

"Both sides did all they could for strategic ambiguity without compromising on their basic positions," said Mr Kuni Miyake, research director at the Canon Institute for Global Studies, a Tokyo-based think-tank.

Japanese Foreign Minister Fumio Kishida and his South Korean counterpart Yun Byung Se announced the deal at a joint news conference after a meeting in Seoul in the final days of 2015, which marked the 50th anniversary of the normalisation of diplomatic ties and the 70th anniversary of the end of World War II.

Japanese Prime Minister Shinzo Abe and South Korean President Park Geun Hye confirmed the agreement via telephone talks. In Tokyo, opposition parties such as the Democratic Party of Japan and the Japanese Communist Party welcomed it as well.

The accord includes Japan's acknowledgement of "responsibilities" for the suffering of so-called comfort women, Mr Abe's "most sincere apologies and remorse" to them and Japan's contribution of 1 billion yen (S$12.2 million) to a fund to be set up by the South Korean government to provide support for the 46 surviving victims.

South Korea said that it "will strive to solve" Japan's calls for a statue of a girl symbolising comfort women in front of the Japanese Embassy in Seoul to be relocated, and that Seoul will refrain from accusing or criticising Tokyo over the comfort women issue in the international community, including at the United Nations.

GREY AREAS IN COMPROMISE

Experts point out that the acknowledgement of responsibilities without adjectives such as "moral" has created room for the South Korean government to explain to its people that Japan addressed its legal responsibilities in its apology and aid for the former comfort women, as demanded by South Korea's civil society.

Similarly, Japan's pledge to allocate 1 billion yen from its national budget to the envisaged fund can be interpreted in South Korea as Japan agreeing to pay government compensation.

Tokyo, however, maintains that a 1965 treaty that normalised diplomatic ties with Seoul legally settled all claims to individual compensation. The reference to "responsibilities" in the agreement therefore, to Tokyo, does not mean legal responsibilities.

Indeed, the Canon institute's Mr Miyake compared the reference to responsibilities to "moral responsibilities" that then Japanese prime minister Junichiro Koizumi mentioned in a letter he sent to former comfort women in 2001.

Mr Miyake said it was significant that South Korea had declared the issue "resolved finally and irreversibly" because the country had kept moving "the goal posts" despite Japan's efforts to address historical issues. These efforts included the issuance of official apologies and provision of money and welfare services to former comfort women through the Asian Women's Fund, a pool of private donations set up at Tokyo's initiative in 1995.

Before finishing its activity in 2007, the fund provided 2 million yen in "atonement money" each to 61 former comfort women in South Korea, 211 such women in the Philippines and 13 in Taiwan. But Seoul said that because the initiative was not purely official, the money could not be considered state compensation.

POTENTIAL STUMBLING BLOCKS

However, experts say Japan will find it difficult to implement the accord if the South Korean government fails to convince the Korean Council for the Women Drafted for Military Sexual Slavery by Japan to relocate the girl's statue. The council is a leading civic group demanding Japan's apology and reparation for the former comfort women, an issue related to the country's 1910-1945 colonial rule of the Korean Peninsula.

"The Japanese public would probably not allow the government to hand 1 billion yen to South Korea if the South Korean government were to say the statue cannot be relocated," said Mr Hideshi Takesada, a professor of Korean affairs at Takushoku University in Tokyo.

Tokyo has demanded that Seoul remove the statue in accordance with the Vienna Convention on Diplomatic Relations, which requires the receiving state to prevent any disturbance of the peace of a diplomatic mission or impairment of its dignity.

Mr Takesada said Japan is also watching whether South Korea will halt moves to submit materials related to comfort women to the Memory of the World Register of the UN Educational, Scientific and Cultural Organisation, jointly with China. "Japan has thrown a ball into South Korea's court," he said. "Seoul, as well, must work hard to get the deal rolling and achieve reconciliation."

Dr Lee Seong Hyon, an assistant professor of East Asian affairs at Kyushu University in Japan, suggests that the two governments should establish a task force to implement specific follow-up measures.

"The current settlement includes a lot of strategic ambiguity, creatively engineered for political expediency," Dr Lee said. "If left unattended, this will become a Pandora's box later."

The South Korean scholar also urged the Abe government to manage what he calls "Japan's right-wing deniers".

"For instance, Mr Abe's apology should not be later demoted to his 'personal' apology, or some ranking Japanese official disowns Mr Abe's apology," he said. "This had been the source of South Korea's questioning the sincerity of Japan's apology in the past."

While the accord, if implemented, will remove what Ms Park has described as "the biggest obstacle to efforts to improve bilateral ties", much work lies ahead. The two sides have yet to work out details such as when South Korea will launch the fund and what kind of projects will be undertaken to, as Japan says, "recover the honour and dignity and heal the psychological wounds of all former comfort women".

•The writer is assistant editor of the world services section in the international department of Japanese news agency Kyodo News.