TOKYO — It would be hard to find anyone more qualified to lead Japan’s national karate team than Rika Usami.

She is a third-degree black belt and won a 2012 world championship. She is a bona fide celebrity in the sport, with videos of her performances racking up tens of millions of views. She even wrote a dissertation on the art of punching.

Yet with karate making its Olympic debut in Tokyo, her sudden elevation in May shook the sport in the land of its birth. Unlike her predecessors, she is young, female and willing to challenge the conventional wisdom of a discipline that is traditional, some would say, to a fault.

“I was shocked by the decision,” said Ms. Usami, 35, speaking from her home in western Japan. “It was something that no one had ever even considered.”

Her appointment, which came after her predecessor was accused of injuring an athlete with a bamboo sword during training, has crystallized a decades-old question in Japan.

Is karate a traditional martial art, a tool for forging the body and tempering the spirit? Or is it a modern competitive sport, a showcase for elite athletes, with a place in today’s Olympic Games?

To many conservatives in Japan, karate and other Japanese martial arts represent values like self-sacrifice and deference to authority that they believe are fundamental to the national character and see as critical to the country’s rise from the ashes of World War II.

But that romanticized vision of a virtuous warrior code — known as bushido, or “the way of the warrior” — has also had a dark side: overwork, harassment and an intense pressure to conform that, in extreme cases, can lead to death.

For karate, whose roots go back hundreds of years to the southern islands of Okinawa, the decades-long quest for Olympic acceptance has involved negotiating a delicate balance between preserving the positive aspects of its tradition and meeting the needs of a modern sport.

That has meant creating new rules, new training regimens and new ways of managing the relationship between athletes and coaches, said Hironobu Tsuchiya, a professor of sports psychology at Osaka University of Health and Sport Sciences who has advised the Japanese Olympic Committee.

“Is karate a martial art or a sport? Each has different objectives,” he said. The first is “about cultivating your humanity. Participating in competitions is just one aspect of that process. But sports are about being faster, higher, stronger. It’s a huge gap.”

Even as karate practitioners from around the globe prepare for three days of Olympic competition starting on Thursday, the debate over bridging that divide, or whether it is even a goal worth pursuing, rages on.

Finding an answer is perhaps more pressing than ever. Globally, karate faces ever more competition from other martial arts. Kung fu is flashier. Krav maga, from Israel, is more practical. Taekwondo and judo are better established as competitive sports. And jujitsu, thanks to the success of mixed martial arts contests like the UFC, is the choice for people hoping to go professional.

For karate to prosper in this crowded environment, it needs to sand off its rough edges and become more universal, said Kazuyoshi Ishii, a karate master and promoter who started Japan’s full-contact K-1 fighting tournaments in the early 1990s as a way to spotlight karate.

In recent years, as K-1 has been eclipsed by the more hard-core spectacle of UFC, Mr. Ishii’s vision for karate has become more family, and business, friendly.

“Visa won’t sponsor a sport where people’s faces are covered in blood,” he said during a recent interview. “Parents don’t want to put their kids in a class where they’re getting hurt.”

Over the centuries, karate practitioners selected techniques for their effectiveness in combat. But moves chosen for maximum lethality are impractical for competitive tournaments.

Before now, that disconnect had helped derail multiple attempts to get karate into the Olympics. It barely made the cut even in its home country, sliding into the lineup only at the last minute thanks to interventions by powerful political figures like Yoshihide Suga, the current prime minister and a former karate practitioner.

The conflict between karate’s old and new guards burst into public view in May, when one of the Japanese national team’s star athletes, Ayumi Uekusa, accused her longtime coach of harassment.

In a statement, she wrote that he had injured her eye during a training session in which he tested the team members’ techniques by attacking them with a bamboo sword. He continued using the sword in training despite repeated requests that he stop.

Ms. Uekusa’s accusations quickly became headline news, forcing Japan’s national team to oust the coach, Masao Kagawa. He said at the time that he was taking “complete responsibility” for his training methods but that he had not intended to hurt anyone.

With the Olympic organizing committee drowning in accusations of misogyny after its leader made sexist comments that forced his resignation, the national karate team chose Ms. Usami as the new coach.

Her selection for a position that had traditionally gone to gruff men well into their 50s was intended to show the world that karate, and Japan itself, is embracing diversity, said Toshihisa Nagura, the general secretary of the World Karate Federation.

Ms. Usami’s interest in the sport goes back to her childhood, when she fell in love with a television show about a young woman who saves the world with martial arts.

But rather than pursuing combat, she became a specialist in kata — fixed sequences of solo movements, much like a gymnastics routine, that are judged on a practitioners’ speed, strength, technique and focus. (Kata is one of the two Olympic karate events, along with kumite, which involves sparring against an opponent.)

Ms. Usami quickly rose to the top of the sport, winning national tournaments at the high school and college levels. At the 2012 World Karate Championships in Paris, she won a gold medal for a routine that combined absolute stillness with kicks and punches so quick and powerful that her uniform whip-cracked around her, echoing through the stadium. The audience gave her a standing ovation.

She retired soon after and started a master’s degree in sports science. She focused on demystifying karate, exploring ways to quantify techniques that traditional instructors had wrapped in esoteric, metaphysical concepts like ki — an abstruse life force that originated in Chinese Daoism.

Ms. Usami has used computer-aided video analysis to refine her techniques and has prioritized athletes’ mental health, a radical notion for a discipline whose idea of sports psychology has long been to shout louder.

The changes have been effective, said Mr. Nagura, the World Karate Federation official.

“She’s able to teach athletes in six months or a year a skill that would have once taken 10 years to learn,” he said.

As karate navigates the old and new, the process of making it an Olympic-caliber sport remains unfinished. It will not appear in the upcoming Paris Olympics, even though France, at half of Japan’s size, has three times as many practitioners.

Yuko Takahashi, a former member of Japan’s national team who runs a karate dojo in Tokyo, welcomed Ms. Usami’s promotion, but questioned whether karate would make meaningful changes.

After years of frustration with karate’s governing body in Japan, she started her own group to promote a more diverse and student-centered vision for the sport. She learned, she said, that “it is incredibly difficult to change the organization, especially as a woman.”

When Ms. Usami talks about the sport’s future, she argues that, just as when performing a kata, the most critical element is balance.

“It’s important to see karate as a sport. And also as a martial art,” she said. “It’s precisely because those two parts exist that karate is karate.”