One such example of Japan backtracking on its apologies came this week, when Prime Minister Yoshihiko Noda said Monday there is no proof showing that Korean women were coerced into sexual servitude for Japanese troops during the 1910-45 occupation of Korea.
The remark, along with a series of similar statements by other senior Japanese officials, including Jin Matsubara, chairman of Japan's National Public Safety Commission, bolstered the long-standing impression among South Koreans that Japan is an unrepentant neighbor.
Matsubara even said that Japan should think about revising a 1993 apology that the country's then-Chief Cabinet Secretary Yohei Kono issued for the forced sex slavery. The so-called "Kono statement" has been considered a key element of the basis for relations between the two countries.
Former Prime Minister Shinzo Abe also said his Liberal Democratic Party would seek to revise past statements of apology if it takes power in general elections expected to take place later this year.
"Revising the Kono statement would mean that Japan gave up on efforts for better relations with South Korea," said Yun Deok-min, a senior analyst at the Institute of Foreign Affairs and National Security, though he said he believes such chances are not high.
The statements of Noda and other senior Japanese officials about the sexual enslavement issue are a "self-inflicting" strategy aimed only at rallying domestic political support "no matter what the rest of the world thinks of" Japan, the expert said.
Historians say up to 200,000 women, mostly Koreans, were coerced into sexual slavery at front-line Japanese military brothels during World War II. Moreover, former sex slaves, who are euphemistically called "comfort women," have long testified the hardship they were forced into.
It is one of the most emotional and unresolved issues between South Korea and Japan.
Seoul has increased pressure on Tokyo to resolve the grievances of the victims, saying the issue is becoming increasingly urgent as most victims are elderly, well over 80 years old, and may die before they receive compensation or an apology from Japan.
Currently, there are only 60 victims alive.
Japan, however, has been ignoring Seoul's demand for official talks on compensating the aging Korean women, claiming all issues regarding its colonial rule were settled in a 1965 package compensation deal under which the two countries normalized their relations.
The Japanese leader repeated that stance on Tuesday.
Noda's denial of coercion in the sexual enslavement added fuel to the already-high tensions between the two countries since South Korean President Lee Myung-bak made an unprecedented visit on Aug. 10 to the country's easternmost islets of Dokdo. Japan has claimed the East Sea islets as its territory.
"The Japanese prime minister and government officials have made very inappropriate remarks about the issue," Foreign Ministry spokesman Cho Tai-young told reporters on Tuesday.
"As a leader, denying the enforced nature of the sex enslavement, which is a serious criminal act that infringes upon womens' human rights, is nothing but a nullification of the country's own apologies and self-reflection," Cho said, urging Tokyo to take "sincere measures."
Referring to reports by United Nations Special Rapporteurs on violence against women in 1996 and 2003, as well as the 1998 U.N. report by Gay McDougall, the spokesman stressed that sex slavery is a matter of universal human rights recognized by the international community.
Cho also hinted at raising the issue to the U.N. General Assembly "at the proper occasion," without further elaborating.
A day earlier, Seoul's foreign ministry officials also refuted the remarks of denial by Japanese politicians, calling them "deeply disappointing."
Along with the sexual enslavement issue, South Korea views Japan's claims to Dokdo as matters related to the brutal colonial rule, not a territory issue. Seoul says Japan's claims to Dokdo amounts to denying Korea's rights because the country reclaimed sovereignty over its territory, including Dokdo and many other islands around the Korean Peninsula, when it regained independence.
South Korea has kept a small police detachment on Dokdo since 1954.
After the landmark trip to Dokdo, Lee also said he decided to make the trip to show through action that Japan needs to sincerely atone for its past wrongdoing, and that the lack of progress in efforts to resolve colonial-era issues, including the sexual slavery, has kept South Korea from fully opening its heart to Japan.
On Tuesday, South Korea's envoy on the comfort women issue said the country will step up pressure on Tokyo to resolve the matter, saying it is an issue related to the universal values of mankind as well as Japan's national dignity.
"Japan has been inert over the wartime sex slavery matter, though Seoul has been calling on it to take due responsibility for the atrocities," Ambassador Kim Young-won said in an interview with Yonhap News Agency. "We have been proactively putting forth various ways against Japan's inaction and will continue to do so."