Osamu Sato, the world super-bantamweight champion, is preparing to defend his title in another bout. Mr. Sato's success in the ring has made him one of Japan's most popular athletes, and is drawing new fans to boxing.

Japan's newest sports sensation works out at his Tokyo gym. Osamu Sato, a 25-year-old with dyed blond hair, beat a rival from Thailand in May to take the World Boxing Association's super-bantamweight title. His victory, along with his quiet manner and good looks, make him Japan's most recognizable boxer. "When I wore the champion belt in front of a large crowd, I was extremely happy," he recalled. "I cannot express how content I was."

The championship fight was particularly tough because it came just three months after he lost his first world title bout. It is unusual for bouts to be so close together. Mr. Sato credits exhausting training, which drained seven kilos off his slight frame, with helping him win.

Now the champ is training to defend his super-bantamweight title on October 9. He fights France's Salim Medjkoune in Tokyo. Mr. Medjkoune has a record of 38 wins, three losses and one draw. In his seven years as a professional boxer, Mr. Sato has piled up 26 wins with one loss and two draws. He fights as a super-bantamweight with a maximum weight of 55 kilograms.

"Boxing has become everything about my life now. My goal now is to win more," he says. To achieve that goal, he has given up most of the pleasures young Japanese enjoy. Mr. Sato does not drink alcohol or smoke, and he seldom goes out.

He was born in 1976 in the city of Kobe. He says his older brother, who likes wrestling, influenced his career. "My brother and I always watched wrestling on TV in our childhood. So I naturally got interested in that," he said. "I did not want to go to high school but my parents forced me to go. I wanted to have a target I could enjoy there. I chose boxing because it is my favorite sport, and joined a well-known boxing club that belonged to the high school."

Mr. Sato won a regional school tournament, a victory that propelled him into a professional career.

After graduating from high school, he joined a famous boxing gym, Kyoei, in Tokyo, figuring a top gym would give him the best chance at becoming a world contender.

But life in Tokyo was difficult. Mr. Sato had few friends and found the city lonely. "Daily training at the gym was very tough. I also worked at a restaurant to earn money," he said. "I was physically and mentally tired every day."

The work, however, paid off. And now his success contributes to boxing's growing popularity in Japan. Mr. Sato is a media sensation, with his face splashed on the covers of fashion magazines. He pops up frequently on popular television shows.

Mr. Sato adds to boxing's popularity, especially by drawing more women fans, says Junichi Hirata, managing editor for Boxing magazine, Japan's best-known publication in the sport.

"He has many female fans," says Mr. Hirata. "He also has many male fans because his fighting style is exciting."

According to the Japan Pro Boxing Association, the country's first boxing match took place in 1887, when two foreigners fought in central Tokyo.

Since that first bout, 47 world champions have come out of Japanese gyms. More champions may be coming, inspired by Mr. Sato. Gyms report an increasing number of people are joining boxing classes. Even women are climbing into the ring, with a few going professional. Boxing magazine's Mr. Hirata thinks Mr. Sato's popularity could bring even more women into gyms.