Boxing Star Ken Ōnuma Talks Strategy, Ambition, and His Ali Inspiration

A monster has appeared in Japan’s heavyweight boxing scene!

Visiting Kakubeni Hōseki Boxing Gym near JR Ōtsuka Station, the explosive sound of mitt work—thud, thwack!—echoed out onto the street.

Holding the mitts was Kyōtarō Fujimoto (39), a former WBO Asia Pacific heavyweight champion and a leading figure in Japanese heavyweight boxing. Throwing massive punches toward him was Ken Ōnuma (21), a Japanese heavyweight prospect with a stunning physique—192 cm tall and over 90 kg—born to a Nigerian father and Japanese mother.

Despite having less than two years of boxing experience and no amateur background, Ōnuma made his professional debut in the “Phoenix Tournament: Asia Heavyweight Challenge Cup,” competing for a first-place prize of 10 million yen, and has remained undefeated in his first three bouts. He advanced to the finals, set for December 18 at Korakuen Hall.

Interestingly, Ōnuma has a surprising background: he was a member of the prestigious Teikyo High School soccer team and is currently a third-year student at Kogakuin University’s Department of Advanced Engineering, studying environmental chemistry and pollution.

“I initially thought I’d play as a forward in the high school soccer championship and maybe even pursue soccer professionally afterward,” he revealed.

“But I underestimated the level at a top school. On top of that, I suffered injuries like an ACL tear in my knee, so I spent most of high school rehabbing and couldn’t play in a single official match. I felt frustrated and powerless.”

After quitting soccer, he shifted focus to university. During the winter of his first year, while tutoring middle school students in math and science, a friend introduced him to boxing.

“My knees had healed, so I thought I’d just move my body a bit, but I found it exhilarating. I could see myself improving every day. While my friends were preparing for job hunting, I was completely absorbed in boxing.”

Currently, he trains physically five days a week and practices at Kakubeni Gym three days a week.

The heavyweight division is the most prestigious and commercially prominent class in boxing, but for Japanese fighters, it has long been considered an unfertile division due to physical disadvantages. Even finding sparring partners in Japan is difficult, but Ōnuma is fortunate to be trained by Fujimoto, who once challenged former IBF champion Daniel Dubois (28).

“Despite his athletic ability, he’s very teachable. At 21, he’ll ask, ‘What should I do?’—rare for someone his age. He can move his nearly 100-kg frame well, and he respects his opponents. There are world-class fighters over 2 meters tall, and the top five are on a different level, but Ken has the potential to become a world-ranked boxer,” Fujimoto said.

Ken Ōnuma also possesses the kind of stoic dedication reminiscent of Shohei Ohtani

Susumu Doi (55), a physical trainer who has supported many top fighters—including former world champion Takashi Uchiyama (46)—is another expert impressed by Ōnuma’s potential.

“Because he had no prior experience, his growth curve with each fight is incredible. His stamina is already at a world-class level. In an era where Rui Hachimura (27) excels in the NBA and Shohei Ohtani (31) thrives as a two-way player in MLB, it’s not surprising that a Japanese heavyweight boxer could compete on the world stage. Ken is serious, hardworking, and lives a stoic life of just going between home, school, and the gym—something that reminds me of Ohtani,” Doi said.

Rather than raw power, Ōnuma relies on elegant footwork and a piercing jab. Doi even likens him to the legendary heavyweight champion Muhammad Ali. Indeed, Ōnuma’s greatest assets are his jab and seemingly limitless stamina.

“Doi-san encouraged me to watch Ali’s fights, and I realized how cool his strength and his big personality are. It would be amazing to become a fighter who can verbalize and achieve ‘I will be champion’ like Ali. At the tournament press conference, I wanted to say I’d box like Ali—float like a butterfly, sting like a bee—but I was too nervous to say it (laughs). Maybe I’ll say it if I win the next fight.”

Ōnuma’s final opponent is the 116-kg giant Mahan Hailey Nuurtai from China. Closing the nearly 10-kg weight difference will be crucial.

“I’ll use my jab and stamina to wear him down and knock him out,” Ōnuma says confidently.

The view he couldn’t reach on the soccer field, Ōnuma now aims to seize with his fists.