Prime Minister Fumio Kishida's first visit to South Korea since taking office in October 2021 underscored that bilateral ties have recovered from their lowest level in decades, but conservatives in Japan may hinder further progress.
With the security environment deteriorating in East Asia amid North Korea's nuclear and missile threat, Yoon Suk Yeol, who became South Korean president in May 2022, has been trying to achieve reconciliation with Japan despite backlash at home.
Kishida has also extended an olive branch to Seoul before the Group of Seven summit in Hiroshima later this month, as the United States has been wary of the adverse impact on regional security of frayed relations between its Asian allies.
In early March, Yoon proposed a solution to a wartime labor compensation dispute that had exacerbated Japan-South Korea tensions for the past years. Later in the month, he made the first trip by a South Korean president to Tokyo in four years for talks with Kishida.
But policies seen as hostile toward Tokyo implemented by Yoon's predecessor Moon Jae In have led to negative perceptions of South Korea in Japan, making it more difficult to boost bilateral ties through cultural interactions and economic cooperation.
On the domestic political front, Kishida might start to adopt a hardline position against South Korea in a bid to garner support from conservatives, with speculation rife that he will dissolve the House of Representatives for a snap election soon after the G-7 summit.
In Japan, many conservatives have traditionally sought to downplay the country's responsibility for its 1910-1945 colonial rule of the Korean Peninsula, while bashing Seoul for often overreacting to historical and territorial issues.
Since he became premier, Kishida, head of a dovish faction within the ruling Liberal Democratic Party, has taken several policies catering to conservatives, including a pledge to strengthen Japan's defense capabilities, aiming to solidify his power base.
An LDP lawmaker said Kishida's approach toward South Korea "could change down the road" if public opinion becomes tougher against the neighbor, adding that further improvement in relations between Tokyo and Seoul "may not be possible" in that case.
In 2018, the South Korean Supreme Court ordered two Japanese companies -- Mitsubishi Heavy Industries Ltd. and Nippon Steel Corp. -- to pay damages to plaintiffs over their alleged forced labor during World War II.
The firms refused to comply with the rulings, as the Japanese government has consistently argued that all issues stemming from its colonization of the Korean Peninsula were "completely and finally" settled under a bilateral agreement signed in 1965.
Following Yoon's proposal, a South Korean government-backed foundation will pay compensation instead of the Japanese companies that were sued. His solution does not require a fresh apology from Tokyo to the plaintiffs, sparking disapproval in the nation.
The Kishida administration has also been reluctant to release a new official statement expressing remorse over Japan's wartime aggression in Asia as previous ones have already done so, in an apparent consideration of conservatives within his party.
On the day before the Japan-South Korea summit in Tokyo on March 16, a conservative group comprising more than 80 LDP parliamentarians out of a total of around 380 requested Kishida not to make any hasty concessions to South Korea.
Hideki Okuzono, a professor of international relations at the University of Shizuoka, said Yoon made a "politically risky decision" over the wartime labor compensation issue, given that anti-Japan sentiment is deeply ingrained in South Korea.
As a gesture of reciprocity for Yoon's "courage," Kishida should have offered a "sincere apology" to South Korea in his own words to accelerate the momentum of improvement of bilateral ties, Okuzono said.
Even if the wartime labor dispute is resolved, the two countries are likely to continue facing various bilateral issues, such as the over the Seoul-controlled, Tokyo-claimed Takeshima islets in the Sea of Japan, and South Korea's alleged radar lock-on of a Japanese defense force patrol plane in 2018.
"Both Japan and South Korea are prone to radical public opinion toward each other, and how to control this is also an issue," said Ken Jimbo, a professor of international security at Keio University.
A survey conducted by Kyodo News in March showed that the younger generation does not expect for improvement in Japan-South Korea relations, with about 75 percent of respondents in their 30s and below answering that bilateral ties will "not change."
Another LDP lawmaker said Japanese young people appear to become more right-leaning recently as they have been disappointed by left-wing opposition parties that have failed to hammer out effective economic policies to benefit them.
Should Kishida strive to capitalize on support from young voters, the possibility cannot be ruled out that he will begin to take a conservative posture against South Korea.
Some foreign affairs experts, however, brushed aside such a view, as Kishida said his heart "aches" over Korea's colonial-era history at a joint press conference with Yoon after their summit in Seoul on Sunday.
Kishida's remarks may be a "sign of Japan's attempt to support Yoon's hard work, which has received harsh criticism in South Korea," said Junya Nishino, another processor at Keio University.
"If both countries make efforts to gain understanding from their respective public opinions, it is possible to further improve ties" between Japan and South Korea, he added.