JUST HOURS before South Korea's president arrived in Japan, Japanese officials were meticulously explaining why it was out of the question for the emperor to satisfy insistent Korean requests that Japan finally apologize for its colonial aggression between 1910 and 1945. Welcoming President Roh Tae Woo, however, Emperor Akihito broke through decades of Japanese stiffness and arrogance and offered his country's first explicit apology for its imperial past. Japan's prime minister then pledged to ease the difficulties of affected Koreans, including the large resident alien population of children and grandchildren of Koreans brought involuntarily to Japan as slaves before World War II.

The emperor's words were more than a courtesy to a visitor. Japan's imperial depredations are still the stuff of deep emotion across Asia. Yet within Japan itself, recollections of colonial brutality have tended to fade into an impression that Japan was not so much aggressor as victim in a war that left the country devastated and alone. Textbooks, for instance, are notorious for stinting the subject. The prevailing amnesia has galled the actual victims of Japan's war machine, and the matter rested more or less uneasily for decades. But in recent years, as Japan has reached beyond its own recovery for a larger regional economic and political role, a demand has been generated for a more generous and historically balanced response. Germany, which has taken major steps to come to terms with its Nazi past, is often cited as the relevant model.

In 1984 Korea's then president visited Japan seeking an apology from the still-ruling emperor, Hirohito, in whose name the earlier colonization had been conducted. Hirihito said it was ''regrettable that there was an unfortunate past between us'' -- words which met an unbecoming Japanese wish not to be seen to ''kowtow'' to Korea and which left Koreans understandably resentful that no direct apology had been made.

Last week Hirohito's son Akihito took the plunge, acknowledging that Korea's sufferings had been ''brought about by my country'' and expressing the ''deepest regret.'' Prime Minister Toshiki Kaifu added ''sincere remorse and honest apologies'' for ''Japanese actions {which} inflicted unbearable suffering and sorrow on the people of the Korean peninsula.'' They are brave and wise words, and they light a path to Japan's deeper reconciliation with its neighbors and itself.