TOKYO -- Imperial congestion will strike this city's two airports today as one of the largest gatherings of heads of state in the world arrives for the biggest show that Japan has ever put on: a 10-day, $90 million party to celebrate the ascension to the Chrysanthemum Throne of Emperor Akihito, a little-known, cautious and solitary 56-year-old man who writes poetry and studies tropical fish.

Vice President Dan Quayle, Prince Charles and Princess Diana, Philippine President Corazon Aquino, Austrian President Kurt Waldheim, French Prime Minister Michel Rocard and other kings, queens, crown princes, prime ministers and presidents, representing 158 nations in all, will assemble tomorrow at 1 p.m. at Tokyo's Imperial Palace for the half-hour enthronement in which 2,500 guests will crane their necks in cramped ceremonial halls to see Akihito, in silk robes valued at $64,000, take his place as the 125th emperor of Japan. Only Afghanistan and North Korea, countries that Japan does not recognize, have not been invited; Iraq was initially invited, but then uninvited.

Akihito's wife, the Empress Michiko, a commoner the emperor met on a tennis court, who is said to have recently come into her own after long, emotionally stressful years of torment by her mother-in-law and a chief lady-in-waiting, will ascend her own smaller throne, called the Michodai. She will wear a five-layered robe of silk damask valued at $100,000.

The enthronement, paid for by the government, reflects the importance that Japan's conservative ruling party places on imperial tradition, and its willingness to put on display a nation that it feels should no longer apologize for its role in World War II -- when Japan carried out its military aggression in the name of the emperor. The enthronement also reflects Japan's role as an economic superpower and banker to the world; many of the invited guests, after paying their respects to the emperor, will ask for financial assistance in meetings with Japanese officials. "Everybody is coming with their hand out," said Robert Orr, the director of the Stanford Japan Center and the author of a recent book on Japan's foreign aid.

Behind the scenes, as with any large party, there is chaos.

"This place is a zoo," one Foreign Ministry official remarked to an American friend last week, referring to the fact that so many governments had requested meetings with Prime Minister Toshiki Kaifu that paralysis had struck all decision-making. For the past months, more than 150 Foreign Ministry officials have been crowded into a single auditorium, working until midnight on the diplomatic complications of having 1,000 foreign guests and entourages in town.

Protocol officials have been trying desperately to work out the seating for 350 guests at the emperor's banquet after the enthronement in the Imperial Palace, where there is almost no room for interpreters. Guests, who had been sent telexes requesting information on food preferences, blood type and languages spoken, were being matched up at tables according to linguistic ability.

"You can imagine how difficult it is," said Yoko Yajima, a protocol officer who has been working on the enthronement arrangements for the past year. President Suharto of Indonesia, who speaks only Indonesian, stumped everyone; finally officials decided that room had to be made for a Japanese-Indonesian interpreter. Suharto's entourage, meanwhile, had booked 120 rooms at the Imperial Hotel. "It's a big delegation," the hotel's president, Ichiro Inumaru, somewhat unnecessarily observed. The king of Bhutan had reserved 30 rooms, and the president of Brazil, 25. Suites suitable for heads of state at the Imperial Hotel cost $2,000 a night. The Japanese government has agreed to pick up the hotel and meal tabs for three nights and four days for one invited representative of each country, a spouse and two accompanying staff people. Each country also gets two cars and drivers for use during the celebration, as well as one or two security men; airfare is not included. Total cost to the Japanese government for accommodation of state guests is $7.8 million.

The largest chunk of the enthronement budget is for security, which was recently increased to $32 million. In Tokyo, 36,000 police will be on duty during the celebrations to offset expected violence by leftist groups opposed to the enthronement, particularly the Chukakuha, an urban guerrilla organization committed to war against the monarchy. Last week, bombs at two Tokyo police stations killed a police officer and wounded six others. No group claimed responsibility, but police believe the bombings were committed by leftists opposed to the enthronement.The last enthronement of a Japanese emperor was in 1928, when Hirohito, Akihito's father, ascended the throne in a ceremony attended by diplomats but not world leaders. (Akihito, who became emperor upon Hirohito's death in January 1989, has had to observe a long period of mourning before his official ascension to the throne.)

This past week, Japanese television has been constantly airing old film clips of the former emperor, as well as romantic footage of the present imperial couple waltzing and one particularly controversial shot of the Empress Michiko cooking in her kitchen. At the time, this much scandalized her mother-in-law and the other aristocratic ladies of the court, who thought it vulgar that a member of the imperial family should be engaging in an activity meant to be done by servants.

The other television clips aired over and over on Japanese television this week are shots of Brooke Shields, who recently dropped in on the still unmarried Crown Prince Naruhito, of which more later.

The Imperial Household Agency The nucleus of all the planning for the enthronement is the Imperial Household Agency, the all-powerful, mostly impenetrable group of 1,100-odd bureaucrats and intractable aristocrats that runs the lives of the imperial family.

In an enormous office that looks out from the private park on the grounds of the Imperial Palace to the glass and steel high-rises of modern Tokyo is Yoshio Karita, the imperial household's vice grandmaster of the ceremonies. Karita is a career diplomat, gracious and reasonable, one of those people at the imperial household assigned to deal with the outside world. He was No. 2 at the embassy in Washington and arrived in Tokyo earlier this year. Karita insists that the imperial household is changing.

"We are starting a new era with a new team," he says. "People on top are very balanced in their thinking, and very flexible." Those who deal regularly with the Imperial Household Agency, however, say that breaking through the barriers is about as easy as getting into Albania.

At any rate, Karita these days is lugging around a five-inch-thick briefing book containing the most minute details of the ceremony. "If I had saved every paper, I would have a stack two feet high," he says. Descriptions of the clothes to be worn by the emperor and empress during the enthronement and subsequent banquets take up four pages alone. The food to be served is equally detailed. Although the Imperial Household Agency asks that the menu for the imperial banquet not be released until tomorrow, suffice it to say that it is largely French, with Japanese touches.

Ever since the start of the Meiji Era, in 1868, the Japanese imperial family has always served Western food to Western guests at formal occasions. Americans and Europeans naturally find this as odd as if George and Barbara Bush served Japanese food to Japanese guests at the White House, but the custom persists. "In the Meiji era, if someone had come from overseas and been served Japanese food, they wouldn't have touched it," Karita says.

However, Karita and others say that because of the great weight of the occasion, Japanese influences will be added. The meal, for example, will be served on lacquer trays, and in small Japanese dishes. "This is a very big development," says Yoko Yajima, the protocol officer.

A Lonely Childhood The man who ascends the throne tomorrow led, by all accounts, an intensely lonely, unhappy childhood. Separated from his parents at age 3, as required by court tradition so that he would theoretically grow up strong and independent, Akihito was raised by overprotective palace attendants. His principal contact with his parents was in prayer to their portraits each morning, and in person during weekly visits on Sunday afternoons.

"This is an important key to understanding him," says Akira Hashimoto, an old schoolmate of the emperor who is now director and general manager of the Kyodo News Service. "He spent very, very dark days. I saw him once killing insects on a summer night in his own room -- one by one on the table -- with a pencil. He was entirely in solitude."

The emperors of Japan represent the oldest living dynasty in the world, and for most of their 1,300-year history they have been figureheads kept behind the scenes by powerful warlords. But in 1868, a group of young samurai carried out a coup in the name of the emperor and "restored" him to sovereignty, even though they retained the real power and the emperor remained a figurehead. The emperor was made a formal object of worship, in part to enhance the government's legitimacy and justify Japanese military expansion.

In 1945, after Japan's surrender in the war, the leaders of the American Occupation considered eliminating the Imperial system and prosecuting the emperor as a war criminal, but instead decided to retain him, much as the warlords always had, for their own aims: to unify Japan and use him as a rallying point for the Occupation goals. In a new constitution written in English and translated into Japanese under Gen. Douglas MacArthur, the emperor was no longer to be considered a god, but a "symbol of the people and of national unity." Today, the emperor operates like one of the European constitutional monarchs.

The important thing to remember is that up until Akihito was 11 years old, he was considered a sacred being. When he went out in Tokyo, traffic stopped and people prostrated themselves. And yet, even after the Occupation, he was still not allowed to live with his parents. Hashimoto, his old schoolmate, remembers one incident that showed how distant Akihito remained from his father.

It was in high school, where he was carefully educated among friends from the upper classes, that the group of friends to which Hashimoto and Akihito belonged got hold of a Japanese translation of "Lady Chatterley's Lover," at that time banned in Japan. The book passed from hand to hand, including Akihito's. "We got excited about reading the contents," Hashimoto remembers. "We were young and had no sexual experience."

But eventually, Hashimoto's father, who was an official in the very government prosecutor's office that had banned the book, discovered that his son, Hashimoto, had helped pass it on to no less than the future emperor of Japan. Furious, he summoned his son, who was at that moment visiting the future emperor at the imperial villa in Kamakura. Hashimoto told Akihito that he had to go because his father was angry, although he didn't yet know why. Akihito asked if Hashimoto would come back and tell him exactly what had happened. When Hashimoto did -- after a two-hour confrontation and lecture from his father -- the future emperor said, "Oh -- a father! Is that a father?"

"I interpreted his reaction as pure astonishment," Hashimoto says. "He didn't know that an ordinary relationship could even exist between a father and a son."

A strong influence on Akihito during his school days was Elizabeth Gray Vining, a Philadelphia Quaker and a pacifist who was recruited by the imperial family after the war to teach Akihito English and American customs. In the beginning, Vining had to give all lessons to Akihito in the presence of one of the imperial chamberlains. "The simplest questions he seemed unable to answer for himself without seeking their help," she wrote in her book, "Windows for the Crown Prince." "I longed for him to have the experience of doing his work entirely on his own, of daring to make mistakes." Eventually, the lessons were given in private, or with a group of friends. Today, the emperor still keeps in touch with Vining, 88, who lives in Philadelphia.

In 1959, Akihito married Michiko Shoda, the daughter of a millionaire businessman. The two had met on a tennis court two years before at Karuizawa, the exclusive mountain resort northwest of Tokyo; today, a debate continues between the emperor and those of the 1950s Imperial Household Agency over whether the meeting was an arranged encounter or by chance. The emperor -- despite widely published reports and statements by his onetime chief adviser that the Imperial Household Agency arranged after an exhaustive search for the two to meet -- still insists that it was a chance encounter in a tennis tournament and that he, the boy who was denied so much affection as a child, was capable of falling in love.

Whatever the case, Michiko Shoda was a brilliant choice. She was beautiful, intelligent and from a prominent family. But she resisted Akihito's proposals of marriage at first, worried that a commoner would not find a place within the imperial family. Akihito persisted, Michiko gave in, and the Japanese public went wild.

Soon Michiko's concerns about being an outsider within the imperial family were realized. From the very start, she was criticized by her mother-in-law, the Empress Nagako, as an unworthy commoner who dared to breast-feed her infant son and carry him in public. Others in the royal family resented her glamour. Finally, in 1963, the Imperial Palace announced that Michiko was suffering from "great mental strain" and that she was being hospitalized for a first-trimester abortion. The abortion, according to news reports quoting Michiko's doctor at the time, was performed because the fetus was "abnormal and there was no prospect of it developing normally." But four months later, the Imperial Household Agency was forced to publicly deny at an unprecedented press conference the widespread reports in Tokyo that Michiko had suffered a nervous breakdown.

Today Michiko has recovered, although she is still seen as a shadow of the vibrant young woman on the tennis court. Her mother-in-law is now ailing, and Michiko is said to make the important decisions within her own family. She has raised her three children at home, and has seen to it that her two sons were sent abroad, to Oxford, to study. This past summer, her second son, the 24-year-old Prince Akishino, married a wildly popular commoner, Kiko Kawashima, for love.

So far no bride has been found for the 30-year-old Crown Prince, the heir to the Chrysanthemum Throne, although a search has long been underway. Last week, an especially inappropriate candidate, Brooke Shields, secretly met with him in Tokyo. Shields was in town to model diamond jewelry for Harry Winston.

The prince is known to have been taken with her since his days at Oxford, when he allowed a photograph to be taken of his room showing a poster of Shields above his bed.