Precisely what will Emperor Hirohito say at a palace banquet this week before he raises his glass to an unlikely state visitor, South Korean President Chun Doo Hwan, whose people the emperor once counted as colonial subjects?

Many Koreans and Japanese want very badly to know. The question has created diplomatic friction between their two governments and been dissected endlessly in the press and official meetings as Chun's arrival in Tokyo draws near.

South Korea wants an apology for 35 years of subjugation to Japan. It feels no one is more qualified to deliver it than the 83-year-old Hirohito, whose portrait as a young monarch gazed down from walls in countless Korean homes and offices until 1945.

Japanese Prime Minister Yasuhiro Nakasone has already told South Korean journalists that his country is deeply repentant over the "ravages" it caused. The Koreans, however, want it from the man who embodied colonial rule.

"We want the emperor to say something about past days, as a representative of the Japanese people. But also as an individual, as a man," said Choo Yeong Sang, propaganda director for an anticommunist association of Korean residents in Japan.

"To forget the past, we must have his words," he said. Leaders of the two countries hope the visit, the first by a Korean head of state since independence, will draw the two countries closer together and conclude the postwar era of mistrust. Both are close allies of the United States.

The emperor, now frail in the 59th year of his reign, is by law a politically powerless symbol of Japan. But at the same time he is his own man. The Japanese government cannot force him to do or say anything, though it can give advice on issues of national interest.

Palace officials report that the emperor has said nothing whatsoever for the record about Korea in the 39 years since his soldiers and administrators there came home after Japan surrendered to the allies and Korea and its other overseas possessions gained independence.

He has, however, expressed regret for World War II to the United States, laying a wreath at the Tomb of the Unknown Soldier during a visit in 1975. China also received an imperial apology for Japan's 13-year war on its soil when Chinese leader Deng Xiaoping visited Tokyo in 1978.

It is generally expected here that Hirohito will say something conciliatory at the banquet. If his past utterances are any guide, this one will be obtuse, seeming to the western ear a study in understatement.

Perhaps his most extreme example came in 1945, with Japan's cities in ruins, its battle fleet sunk and more than 3 million Japanese dead. Addressing the nation by radio to announce the surrender, Hirohito noted that "the war situation has developed not necessarily to Japan's advantage."

President Chun, who faces criticism at home for visiting a country many Koreans continue to dislike and accuse of economic domination, needs as strong a statement as possible. That way, he can be depicted as the man who finally wrung repentance from the Japanese.

It would also score points for him with the 700,000 Koreans in Japan. Chun's government and Communist North Korea wage a continuing struggle for the allegiance of these people.

According to Japanese Foreign Ministry sources, the South Koreans at first pressed for the emperor to host the visit. The Japanese declined, saying that the prime minister always played that role. However, Seoul newspapers have paired pictures of Chun with pictures of the emperor, as if it will be a meeting between just those two.

Nakasone, meanwhile, would fare better politically if he soft-pedaled his penance. After Korean officials told Japanese reporters that they would welcome an apology, Japanese rightists angrily declared that the emperor owed nothing to his former subjects. Some made threatening phone calls to the South Korean Embassy.

Such critics have an extremist viewpoint. Yet many analysts here feel that mainstream Japanese society lacks a firm feeling of guilt or shame over the country's years at the helm in Korea, a rule that for years was recognized as legal by the western powers.

Nationalistic injustices aside, Japanese rule brought railroads, industry and modern administration to a semifeudal Korea. War damage was comparatively minor. "There are people who will argue that it was the best thing that ever happened to the Koreans -- 35 years of education and development," said a western diplomat in Tokyo.

But Koreans of all political persuasions see the colonial period as one of the darkest chapters in their history.

Communist North Korea has condemned the emperor's expected apology as meaningless on the grounds that Chun does not represent the Korean people. But through the North's ideology runs a thread very similar to the South's: that Korea endured immeasurable brutality, which Japan today must work to erase.

"People over age 50, who lived during the days of the Japanese occupation, suffered in many ways in the name of the emperor," said Hwang Kap Sung, president of a pro-North Korean magazine that is published in Japan.