Eisei Miki, the head monk of Kakurinji Temple in the western Japanese city of Kakogawa, still shivers with anger when he describes the robbery the temple suffered in 2002. Among the stolen goods: one particularly important painting of the Amida Buddha from Korea's Koryo period (918-1392), which the temple had treasured for hundreds of years. Caught last October, the two Koreans responsible for the theft insisted they were on a mission to reclaim pieces of Korean history, which had been appropriated by the Japanese. Worse, the Korean media and public bought the argument. "Have you heard of anything more ridiculous?" asks Miki.

His frustration embodies yet another thorny controversy embroiling Japan and the Korean peninsula: to whom do hundreds of thousands of ancient Korean artifacts in Japan rightfully belong? Koreans accuse the Japanese of plundering the artwork, mostly during their 36-year occupation of the peninsula, and they blame their own government for not seeking the objects' return. Most Japanese consider the issue a dead one, resolved by the 1965 Japan-Korea Treaty, which led to the return of some 1,400 items. To be sure, not all the works were looted; Kakurinji Temple, for instance, received the painting--probably as a gift--long before the Japanese invasion. Nor was the settlement in the 1960s definitive, as it neglected artifacts in Japanese private collections as well as those originating in North Korea. But with cultural relations between Japan and South Korea warming, experts are hoping the dispute can finally be resolved.

Japan is hardly unique in having made off with treasures from a former colony. The best European museums would be empty without looted art. But the size of the haul is astounding. Eighty percent of all Korean Buddhist paintings are believed to be in Japan. And, says Seoul art historian Kwon Cheeyun, "35,000 Korean art objects and 30,000 rare books have been confirmed to be there, too." That's only the tip of the iceberg: much more is believed to be hidden away in private collections.

Historians believe Japan carried away the bulk of its Korean cultural assets during two aggressions: the 16th-century invasion of the Korean peninsula and its 20th-century occupation. Determining legal ownership is far more difficult than with the art looted by the Nazis, for instance. "It's almost impossible to trace the provenance" of centuries-old artifacts, says Toshiyuki Kono, a law professor at Kyushu University. Besides, the Japanese annexation was internationally recognized in 1910; relocating Korean artifacts within "Japanese territory" was lawful at the time. Furthermore, Japan didn't sign the 30-year-old UNESCO convention to prevent trafficking of stolen artifacts until 2003.

--To Korea's annoyance, Japan holds many items of particular value. More than 1,000 bronze, gold and celadon pieces owned by the late businessman Takenosuke Ogura now make up the core of the Tokyo National Museum's Korean section. Another precious item is a two-meter-tall stone tablet, originally built in northern Korea to commemorate the country's repelling of the 16th-century Japanese invasion. The work sits in Tokyo's Yasukuni Shrine, where Japanese politicians occasionally enrage Koreans and Chinese by paying respects to the war dead enshrined there. Last month, South Korea's former prime minister, Lee Han Dong, launched a campaign in Seoul to seek its repatriation. "For both Koreas," says Joo Dong Jin, a civil activist working for the campaign, it is a matter of "national spirit and pride." Yasukuni will return the piece, says a shrine spokesman, once both North Korea and South Korea make official requests through the Japanese government.

While officials on both sides drag their feet, citizens are driving the repatriation movement. Yoon Sung Jong set up Korea's Citizens' Committee for Cultural Heritage Return Movement in 2002 to run promotional exhibits, seminars and a Web site calling for the return of the artifacts. Several Japanese collectors have voluntarily donated their holdings to South Korean museums. The Tenri Central Library in Nara, western Japan, loaned a 1447 painting titled "Dream Journey to the Peach Blossom Land" by the 15th-century Korean master An Gyeon to Seoul exhibitions in 1986 and 1996. Considered one of the most significant Korean paintings of all time, Yoon says the work should hang in Korea. The library, however, maintains that it has never been formally asked for the return of the painting--and declines to say whether it would return the work if it were.

Generational change is also helping soothe tensions. The subject of looted art remains most sensitive to older Koreans. "We are the first generation [of experts] who can be objective," says Hideo Yoshii, a 40-year-old archaeologist with Kyoto University. Young Korean scholars like Pai Hyung Il, an archeologist at the University of California, Santa Barbara, give Japanese credit for first discovering beauty in items like the peninsula's celadon porcelains, which Koreans previously ignored in favor of Chinese antiques, which they considered more valuable. To Pai, demanding the repatriation of all Korean items isn't realistic. Another young academic, Tokyo arts professor Yoko Hayashi, who recently conducted the first comprehensive study of the situation proposes promoting privately held relics exhibits, joint research by the two countries and long-term loans of Japan-owned Korean treasures to Korea.

Still, the issue will not be quickly resolved. And the Kakurinji Temple's painting is still missing--though the Korean thieves were sentenced to jail after a Korean judge failed to buy their patriotic defense. Still, Miki, the head monk, holds no grudges against Koreans. His temple was, after all, founded by a Korean monk in the sixth century and occasionally sponsors events promoting Korean arts. "Our temple is like the oldest symbol of Japan-Korea friendship," he says. That friendship is, once again, being sorely tested.