In the world of behemoths he chooses to inhabit, Chiyonofuji is something of a pipsqueak.

He weighs in at a mere 255 pounds and regularly enters the sumo ring to grapple with flabby, beefy giants who are 50 pounds heavier. It doesn't seem to bother him. Usually it is his heavier opponents who get toppled to the ground or tossed outside the ring. He collects the winner's purse.

Chiyonofuji, 25, is the new superstar of sumo wrestling, the centuries-old sport which Japanese revere as much as sake and festivals. He is the idol of millions who call him urufu, their way of saying "wolf" and one of the fastest-rising stars in the sport's history.

Sumo is still remarkably popular in Japan for athletic reasons and for the aura of traditional pageantry that surrounds it. The rules are the same as when the sport first emerged in the earliest chronicles of the country. The winner is the man who forces his opponent to the earth or throws him out of the circular ring.

Style is everything before the grappling actually begins. Contestants crouch in their loincloths, glare at their opponents, and then burst toward one another seeking holds and positions that have changed little over time.

Histories say sumo first was a divine clashing of muscular giants whose sweaty efforts were dedicated to the gods of Japan. Later, the matches were used in place of battles to determine sovereignty over disputed territories.

Since the 8th century, when the first matches were held in an imperial palace, sumo has had the official patronage of the emperor of Japan and today Tokyo tourrnaments are frequently visited by sons of Emperor Hirohito. Ancient warlords used sumo to train their men for battle.

The Japanese sumo wrestler is far more popular and highly regarded than, for example, an American wrestler. Large corporations vie for the privilege of being known as the sponsor of a popular winner and a long-running favorite is blessed with commercial opportunities comparable to those of a National Football League quarterback in the United States.

Long training hours are rewarded with high pay for the successful wrestler. It is believed that Chiyonofuji makes more than $4,000 a month in television commercials, corporate donations and special sums from bets placed by competing businesses. The actual earnings are well-kept secrets.

There are six major tournaments a year in Japan and each is enormously popular.Each day's matches last several hours. For those able to attend, the hours turn into a festival of food, sake, and beer.

For others, it is a time to gather around the television sets. The major events pitting champions against champions take place late in the afternoon and around 5 p.m. business in many places comes to a halt.

It is estimated that two-thirds of the television sets in Japan were tuned in when Chiyonofuji walked off with the Emperor's Cup from the season's opener in Tokyo after a dramatic playoff bout in which he toppled a veteran hero. As victor, he was promoted to the rank of ozeki, second-highest in sumo's graded system. Experts think that if he gains a little weight and keeps training he will become a yokozuna, or grand champion.

What he lacks in weight, he makes up with speed and power.Unlike most sumo wrestlers, he moves like a boxer, with quick, sudden shifts of his body that send surprised opponents tumbling haplessly out of the ring.

A recent visit to his stable, or training camp, turned up some clues to Chiyonofuji's success. He fought 26 consecutive matches, winning 21, most of them simply by moving faster than his ponderous sparring partners. Backed to the ring's edge in one match, he twisted suddenly, caught the foe off-balance, and casually tossed him out. When another challenger came rushing from the starting crouch, Chiyonofuji merely sidestepped and watched him sail out of bounds.

"Muscle and power and the ability to move fast," is how Chiyonofuji later explained his talents through an interpreter. "I need everything."

He showed his everything late in January when he startled the sumo world by winning 14 straight bouts in the Tokyo tourney, and, on the final day, faced the veteran yokozuna, Kitanoumi, whose record was 13 wins and one loss. In the regulation match, Kitanoumi caught him in a favorite belt grip and simply hoisted him out of the ring, bringing about a tie.

In the sudden-death play-off bout that followed, Chiyonofuji charged back, grabbed Kitanoumi's belt and with one powerful throw of his right arm sent him out of the ring. It was the first time in six years that a sumo wrestler of Chiyonofuji's relatively low ranking -- sekiwake -- had won a major tournament.

It was the kind of performance that Japanese crowds love and he was an overnight hero. Sumo-groupies cluster around his stable waiting for a glimpse. Commercial offers come pouring in. He has proved to be a magnetic and loquacious hero, in contrast to the usual sumo star for whom a grunted monosyllable is considered quite a statement.

"Chiyonofuji is the 'now' kind of wrestler," observes Seigoro Kitade, who has watched them come and go for 28 years as a sumo announcer for Japan Broadcasting Corp. "He is a wrestler who fits today's modern society."

With several sumo veterans retiring this year, along with baseball star Sadaharu Oh, Japan is looking for a new sports king.

"We lack superstars now so the Japanese want to find a new one," Kitade said.

Chiyonofuji's real name is Mitsugu Akimoto; his fighting name means "Mt. Fuji Forever." He came to his Tokyo stable from his home on the northern island of Hokkaido as a comparatively skinny competitor. He had large eyes, a lean, hungry look on his face and an unusually aggressive fighting style. His trainer throught he resembled a wolf. The nickname stuck.

As a youth, he had broken one shoulder bone seven times and another once, a collection of injuries that would have finished many aspirants. Chiyonofuji made up for it by arduous exercises -- lifting barbells and doing 200 push-ups a day -- to strengthen protective muscles around his neck.

Today he can lift 300-pound giants off the floor. But his own weight problem makes him peculiarly vulnerable and he is aware of the weakness.

"The giants can just lift me up," he said.

His defense, once the opponents has a firm grip, is to go for the leg trip, locking one foot behind the other man's leg and pushing him down. He is trying to gain weight and has stopped smoking to increase his appetite.

Chiyonofuji has five or six more years, of top performance left and he could well dominate the sport. Kitade, the broadcaster, thinks he will become a grand champion if he does not get dazed by adulation from the public.

"His biggest enemy is his popularity," Kitade said. "The mass media will take a lot of his time."

Girls and rich patrons will hover around him and he can make a great deal of money through commercial advertisements. "He may lose control," said Kitade. "Popularity can bring such big pressures. He may lose his fighting spirit."