22-year-old tennis star Naomi Osaka made $37 million last year, surpassing Serena Williams as the highest-paid female athlete. Here's how she did it.

Osaka's earnings break the record for the most money earned by a female athlete in a single year. That record, per Forbes, was previously held by Maria Sharapova, who earned $29.7 million in 2015.

Her earnings also ended Serena Williams' winning streak as the world's highest-paid female athlete, a title William held for the past four years. (Osaka earned $1.4 million more than Williams over the last 12 months, according to Forbes.) Osaka ranks in the 29th spot and Williams ranks 33rd among the 100 highest-paid athletes in the world.

Osaka wasn't even ranked on Forbes' 2019 list of highest-paid athletes.

Osaka and her family first lived on Long Island before moving to Florida, the epicenter of youth tennis. She has one sister, Mari Osaka, who is also a professional tennis player. Mari competes in lower-level events and is 18 months older than Naomi.

"We made the decision that Naomi would represent Japan at an early age," Osaka's parents told Tom Perrotta of The Wall Street Journal. "Quite simply, Naomi and her sister Mari have always felt Japanese so that was our only rationale. It was never a financially motivated decision nor were we ever swayed either way by any national federation."

Osaka preferred to play in small International Tennis Federation events, which aren't often televised, instead of junior tournaments. She declined to enter junior Grand Slam tournaments even when her ranking was high enough to qualify, Perrotta wrote.

Sean Gregory for TIME magazine described the junior tennis circuit as "a cutthroat environment that burns out many promising teen players."

Osaka and her sister were largely taught how to play tennis by their father, Leonard Francois, who would take them to public courts.

A recreational player, Francois's tennis dreams for his daughters began when he watched Venus and Serena Williams playing in the French Open on TV, wrote Gregory. He looked to the Williams sisters as models for his daughters and copied the coaching approach their father took.

Naomi and Mari were both homeschooled online so they could dedicate more time to practicing tennis.

She and her father would practice at the Evert Tennis Academy for two hours a day. "She had a lot of raw talent and she hit the ball a ton, but she wasn't moving and she was making a lot of errors," retired pro tennis player Chris Evert, who cofounded the academy, told the Journal.

But when she began training with two professional coaches — first David Taylor, then Serena Williams' former hitting partner Sascha Bajin — Osaka's game improved quickly.

In January 2016 at the Australian Open, Osaka qualified to enter her first Grand Slam, rolling into the third round. She also reached the third round of the French Open and the US Open.

That same year, she became the first Japanese player since 1995 to reach the finals in the Toray Pan Pacific Open, a WTA event in Tokyo.

Two years later, in March 2018, Osaka became the first Japanese woman to win the Indian Wells Masters in California (USA).

Source: Naomi Osaka Profile

Japan's Nationality Act mandates that those who hold dual citizenship must choose one before their 22nd birthday, wrote Cindy Boren for The Washington Post.

"It is a special feeling to aim for the Olympics as a representative of Japan," she told Japanese broadcaster NHK. "I think that playing with the pride of the country will make me feel more emotional."

She supported the decision to push back the Olympics until next year amid the pandemic. "Sport will eventually unite us again and be there for us always, but that time is not now," she wrote in a since-deleted Instagram post, as reported by ESPN.

Procter & Gamble, All Nippon Airways, and Japanese ramen company Nissin all signed endorsement deals with Osaka to use her around marketing for the Games, according to Forbes.

"If you're talking about an international sporting event like the Olympics, she's your international star you're going to market it around," Bob Dorfman, a veteran sports marketer, told TIME last year. "She's got American appeal, Caribbean appeal, Japanese appeal. As nationalities continue to mix in this world, that makes her even more desirable."

After a bidding war with Adidas, who Osaka previously partnered with, Nike reportedly paid Osaka more than $10 million last year in an agreement that runs through 2025, per Forbes. Neither Nike nor Osaka's rep has confirmed the financial details of the endorsement agreement.

It plans to launch an Osaka streetwear line in the fourth quarter and gave Osaka a rare exception to its requirement that tennis players only wear Nike gear during a match.

"Mentally, I feel she's the best female tennis player that I've seen come along since Serena," Rick Macci, a tennis instructor who worked with the Williams sisters when they were young, told the Journal.

Osaka also has one of the fastest serves on record at 125 miles per hour, only slightly slower than Serena's 128 miles per hour serve.

Williams is reportedly Osaka's role model, but Osaka doesn't see herself as the next Serena. "I don't think there is ever going to be another Serena Williams," she told TIME. "I think I'm going to be me. And I hope people are OK with that."