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Her hands move in a blur. Then they stop, frozen like stone.

Sakura Kokumai is 27 years old and could be America’s best hope for a medal in karate at the Summer Olympics in Tokyo.

She has a menacing presence in the dojo, even though she is not quite five feet tall. Somehow, when she puts on her “gi,” or uniform, Kokumai seems to grow.

“Whenever I wear a gi, I feel very strong. I feel confident, and I feel more like myself,” she says.

There are two types of karate debuting at the Tokyo Games. One is sparring, called kumite. The other is a series of precise movements done individually, called kata. “I always explain it as like figure skating without music,” Kokumai says.

She is No. 1 in the U.S. in women’s kata, and she’s top five in the world, winning gold at the Pan American Games last fall and silver at the Karate Premier League Tournament in Dubai last week.

She accomplished all of this without a coach.

Kokumai is living for free with a host family in California. She has no car. Her wardrobe consists mostly of Team USA clothing, and when asked how much money she has in the bank, she hesitates. “A little,” she finally admits with a laugh.

Like thousands of Americans, Sakura Kokumai has given up everything to train for the Olympics in a sport that doesn’t attract many sponsors or much money. But unlike many of those other athletes, she never thought the Olympics could be in her future.

“A lot of swimmers, wrestlers, they will grow up dreaming about the Olympics because they see athletes competing at the Games before,” she says. “For us karate athletes, it was like a different universe.”

Suddenly when the International Olympic Committee decided in 2016 to add karate to the Tokyo games, Kokumai had decisions to make. “Where do I go? Where do I start? What do I do?”

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Training since seven

Kokumai began taking karate lessons at the age of 7 in Hawaii. “My mom kind of threw me into a YMCA class,” she says. She enjoyed the sport and the people. “To me, karate was more of an escape...just something peaceful about it. It was calming.”

Kata in particular attracted her. “It’s less than three minutes, but I felt like I was expressing myself through the kata, so I think I fell in love with the art of it.”

Kokumai says each kata routine is a fixed set of movements that’s been “passed down for years.” What an individual athlete can change “is the rhythm, the timing.”

Kokumai says her small stature allows her “to show more speed” than someone who is taller. “I think strength is my power.”

She became good enough to start competing overseas as a teenager. “It’s been nonstop since then.”

Kokumai eventually went to college in Japan, earning an undergraduate degree in linguistics and education, followed by a master’s in international relations, and she was working in Tokyo when word came down that karate was going to be in the 2020 Olympics. Upon hearing the news, “I didn’t know what to do to train,” Kokumai says. “I didn’t know what it took to get there, because there was no example. It’s the first time, and there was no past karate Olympian.”

Kokumai tried to continue working and training, but found herself falling asleep doing stretches. She wasn’t eating right. “I soon realized that juggling work and karate was impossible. So I decided to quit my job.”

That’s when she moved to California. She trains in the garage at the home where she stays, and she walks to the local gym. “I did find a strength conditioning coach, but he’s in San Diego.”

Once in a while, Kokumai spends around $50 to take an Amtrak train to San Diego, where her conditioning coach lets her sometimes sleep over in the gym.

Could be first and last shot at Olympic gold

Even though Sakura Kokumai has spent much of her life traveling back and forth to Japan, there was never any question in her mind which country to compete for. “I started karate in Hawaii, I looked up to athletes who have represented the U.S.,” she says. “I always identified myself as an American.”

Money, however, is increasingly on her mind. “Because I’m my own coach, I never really had the time to handle the other things, which has been a struggle.”

She recently picked up Panasonic as a sponsor, though she will not reveal what kind of financial help, if any, comes with that. She receives a monthly stipend from Team USA, and the USA Karate Federation reimburses her travel expenses to international tournaments crucial to earning enough qualifying points for the Olympics.

There are no guarantees Kokumai will earn one of the 10 spots for female kata in Tokyo, though she is currently among the world’s best. Only Japan is guaranteed one spot — the remaining nine will be based on an individual athlete’s global ranking.

This could be Kokumai’s only shot at an Olympic medal. Karate will not be in the 2024 Summer Games in Paris. What if all this work and sacrifice is for nothing? Even if she does win gold, is there any financial reward for a kata karate athlete?

“My focus right now is to qualify, and then my thought was, OK, once I get there, then I’ll figure it out,” she laughs.

Maybe after she qualifies, Sakura Kokumai will be able to afford a coach. Or maybe not.

“I just practice and do what I know, and it’s gotten me where I am today,” she says, “so I guess I’m doing all right.”

Disclosure: Invest in You: Ready. Set. Grow. is a financial wellness and education initiative from CNBC an Acorns, the micro-investing app. NBCUniversal and Comcast Ventures are investors in Acorns.