With two Grand Slam wins in the past year, Naomi Osaka has shot to No. 1 in the rankings but offered few clues about what makes her tick.

An ESPN The Magazine collaboration.

One year ago, Naomi Osaka was the 68th-best women’s tennis player in the world. She was prone, in moments of frustration, to screaming, banging her racket, even crying. She would succumb to mental paralysis when a match wasn’t going her way. Or she’d turn into the Hulk, hitting everything bigger, faster and stronger, even when precision was what was needed. She played 21 matches last year in which she lost the first set. She rebounded to eke out a victory in just two of them.

She was 20 years old. She had first picked up a racket when she was 3. But she’d avoided the sport’s junior circuit, and before winning her first WTA title last March at Indian Wells, the toughest opponent she’d ever defeated was her older sister, Mari.

Osaka was a mystery. Some saw an awkward noob, unused to the klieg lights. Others saw a sheltered woman whose personality and opinions appeared unformed. Beyond her being the daughter of a Haitian father and a Japanese mother, little was known about her. She was a cipher with a racket.

Then last September, in Flushing Meadows, Osaka beat her idol, Serena Williams, in a U.S. Open final that will live in the annals of tennis history. Four months later, she claimed her second straight grand slam title at the Australian Open. A star, however reluctant she might have been to show her face, was born.

Now Naomi Osaka is the world’s No. 1—and still very much a mystery.

Her parentage has made her an object of worldwide fascination. Osaka is no longer just Haitian and Japanese. She’s Haitian, Japanese and famous. She’s a symbol of transformation in a sport still robed in a much whiter past. And as she’s shot to prominence, the tennis media and fan base have generated multiple and sometimes conflicting narratives as they try to puzzle her out. Celebrities want to meet her. Sponsors beckon with lucrative endorsement deals. The curiosity that fueled questions such as Who is the girl who beat Serena?—and beyond that, Who is she, period?—has only intensified.

The short answer is this: Naomi Osaka is a Gen Z tennis phenom who’s into Overwatch and Pokemon and Harry Potter and Beyonce and Crazy Rich Asians. Beyond that, she’s almost deliberately unknowable.

In tennis, an opponent can be dangerous if you can’t read her serve. Osaka is dangerous because it is hard to read her.

Two-time Grand Slam champion Naomi Osaka sits down with E:60’s Tom Rinaldi to talk about her rapid rise to fame, and that unforgettable U.S. Open win over Serena Williams.

In December, just a few weeks before she would head to Australia, Osaka went to the Wizarding World of Harry Potter at Universal Studios. She documented the day on Instagram and indulged in some introspection. “I spent the whole day trying to figure out which house I would be between Gryffindor or Slytherin,” she wrote.

It was one of Osaka’s more revealing posts—for Potterheads, at least. Still, the question lingered. One month later, after winning the Australian Open, she tells me she still isn’t sure how to classify herself.

A primer, for non-Potterheads: Slytherin produced the notorious, power-mad psychopath Lord Voldemort. Meanwhile, Gryffindor was home to Harry, the hero of the series. Easy, right? Not exactly. Everyone tends to forget that the Slytherin house also produced Severus Snape, the impossible-to-read double agent who was instrumental in taking Voldemort down.

So is Osaka sending a message about the virtues of being impossible to read? It is, ironically enough, unclear.

On the day after her Australian Open win, Osaka is wearing a multicolored body-con dress by black designer Carly Cushnie. When I ask whether she’d met Cushnie or had procured the dress through a stylist, Osaka stares at me quizzically. She’d bought it online. It still hadn’t sunk in that designers and stylists soon will be clamoring for her to be photographed in their wares, or that when you’re famous, people simply give you things for free.

When I ask whether Osaka would be interested in attending New York Fashion Week, she says yes—but only if it didn’t interfere with her training schedule. And would she want to be on the cover of Vogue? “That would be really incredible, but at the same time, I feel like I would have to work for it, earn it in a way,” Osaka says. She elaborates about how maybe she would need to win four grand slams in a row instead of just two. “I think Serena had 13, 14 before her first one.”

Osaka’s IMG handler interjects: “We’re shooting Vogue next week.”

Has Osaka forgotten that she’d be appearing in the most high-profile fashion magazine in the world? Unlikely. Maybe she’s channeling her inner Severus Snape.

“I don’t think people should know what I’m thinking,” she tells me eventually. “I’m hiding you from my thoughts.”

In Australia, the riddle that is Naomi Osaka was faced with a riddle of her own. And how she solved it was one of the tournament’s revelations.

Su-Wei Hsieh is a Taiwanese player who relies on slices and drop shots instead of raw power. (Osaka’s serve hovers between 115 and 120 mph. Hsieh’s barely cracks three digits.) Hsieh’s seemingly arbitrary variations of pace make it difficult to establish a rhythm and can drive opponents nuts. In the third round in Melbourne, Osaka faced Hsieh for the first time.

Hsieh won the first set 7-5, vexing Osaka, destroying her timing. Osaka racked up 20 unforced errors, the last one handing the set to Hsieh: Osaka slid into a half split for a return and pounded the ball past the baseline. She used her hands to steady herself, then hurled her racket onto the court.

The start of the second set didn’t go much better. Hsieh was up 2-0 and leading 40-0 in the third game. With Osaka standing at her baseline, Hsieh finessed a cross-court shot that bounced just over the net. Osaka’s feet never even moved. Hsieh was leading 7-5, 3-0. The prospect of going home was real.

Slowly and methodically, though, Osaka came back. After each player held serve in the next two games, Osaka won 11 of the last 12 games, taking the second set 6-4 and then breezing through the third set 6-1. She not only took advantage of a deterioration in Hsieh’s serve but grew more assertive—forcing Hsieh to adjust to her style and pace instead of the other way around. “I just started thinking that I’m in a grand slam,” Osaka said afterward, explaining her change in attitude. “I shouldn’t be sad.”

Osaka had reset herself. She had found a way to win. It was, in a way, a breakthrough. She lost first sets twice in Melbourne—once against Hsieh, then in the next round against Anastasija Sevastova—but recovered both times. The road to hoisting the trophy ultimately ran through a series of wrenching, hold-your-breath three-set matches, including a dramatic final against current No. 3-ranked Petra Kvitova.

“It has been like a roller-coaster ride; every match has been like that,” says Osaka’s high-performance coach, Abdul Sillah, the day after Osaka wins in Melbourne. “Which is good, because more than the match itself, more than the victory itself, you’re trying to see if you have a champion on your hand, or if you have a winner. Winners are one-hit wonders, right? But a champion is like Serena, LeBron—can you do this consistently?”

Indeed, since winning the U.S. Open in September, Osaka has shown signs of a psychological growth spurt. It seems evident in her posture—she stands straighter in front of crowds instead of looking as if she’s willing herself to disappear. It shows in the way she fields questions. “She knows she’s funny,” says Osaka’s agent, Stuart Duguid. (Her deadpan rejoinder whenever a reporter asks why she has the surname of her mother instead of her father: “Everyone who was born in Osaka, their last name is Osaka.”)

Psychological growth does not, of course, make a person impervious to what others think. Just 16 days after claiming the Australian Open title, Osaka splits from her coach, Sascha Bajin. Tennis fans are stunned. Her time with Bajin, best known as Serena Williams’ longtime hitting partner, had produced a clear before-and-after effect. With Bajin in her box, Osaka had won her first professional major tournament, at Indian Wells. She won two grand slams. Bajin was named the WTA’s Coach of the Year. Why put the brakes on such a ride?

A few days after that, she loses her first match without him to unseeded Kristina Mladenovic at the Dubai Tennis Championships. After the match, Osaka admits that the outsized reaction to her split with Bajin had seeped into her head. “This match is the result of that,” she tells reporters. “I’m pretty sure as time goes on you guys will stop talking about it. For now, it’s like the biggest tennis news, I guess. It’s a little bit hard because I feel like people are staring at me, and not like in a good way.”

After she won in Australia, a reporter had asked what she and Bajin had discussed before she faced Kvitova. “I didn’t talk to him,” Osaka said, smiling. “We haven’t really been talking, to be honest, like before any of my matches here. He would tell me, like, one thing, then I would be, like, ‘OK.’”

Perhaps what Osaka was telling the world was that Bajin was not the architect of her new mental fortitude, that it’s a mistake to think of her as a talent shaped solely by tennis Svengalis—even one who worked with her tennis idol.

But that’s a whole other thing.

A few days after her win in Australia, Osaka and I are talking in an office at the Evert Tennis Academy in South Florida, where she trains. The room is beige. Sunlight pours in from sliding doors that overlook an array of tennis courts flanked by palm trees. Osaka’s mother, Tamaki, sits silently in the middle of the room in a black leather executive chair.

Partway through the conversation, I decide to broach the subject of the U.S. Open and the infamous cartoon—the one from the Melbourne Herald Sun that depicted Serena as a hulking, tantrum-throwing toddler with exaggerated lips and hair, and Osaka as a thin, dainty, straight-haired blonde. When I do, Osaka’s IMG rep quickly tries to steer the conversation elsewhere. But Osaka is not deterred; her speech, instead, becomes slower and more deliberate: “If I were to put it bluntly, I know that there’s a lot of people that don’t like Serena, and I feel like they’re just looking for someone to sort of jump on to be against her and I feel like they found that in me. Of course, I don’t really like that. … I want people to go with me for the right reasons.”

She lets out a heavy sigh.

“If I’m being blunt, I feel like that’s happened a lot, like after the U.S. Open.”

As Osaka speaks, her facade cracks. Tears begin streaming down her face. Someone hands her a tissue. She dabs at her cheeks. Still, she holds her eye contact with me and continues. She dreamed, she says, of beating Williams one day. She just hadn’t imagined the nightmare that would accompany it.

“I love Serena,” Osaka says. “Growing up … I really loved watching her matches, and honestly, I wouldn’t be where I am without her. That’s a fact. She opened so many doors for tennis and especially for people of color. When you’re little and you’re growing up and you’re watching people, like the Indian Wells thing that happened … ”

(A reminder: In 2001, fans at the California WTA event booed a 19-year-old Serena during the final match after her sister Venus had pulled out just before their semifinal matchup two days prior. Their father, Richard Williams, said spectators directed racist comments toward him, prompting Serena to boycott the tournament for 13 years.)

“For me, that was ‘How can a human be so strong?’ That’s one of the reasons I love her so much.”

The blessing and burden of Osaka’s career is that she is running through doors Williams opened and she knows it. She is not made of stone. She is not oblivious to history. As it was for Serena the past two decades, the reality of Osaka’s work life is that she spends a lot of time being the only black woman in the room. “Tennis is not a black person sport,” Sillah says matter-of-factly. (He would know; before training Osaka, he also worked with Serena.)

Racism tethers them to each other. And they are just enough alike that the comparisons are inevitable—ferocious servers who back up their power with underappreciated tennis IQ. For some, Osaka’s rise marks the beginning of the end of the Williams era, something that can’t come quickly enough. To an ugly part of tennis fandom, part of Osaka’s appeal is that she’s black without constantly reminding everyone of her blackness. She does not wear beads at the end of her cornrows that crackle every time she hits a ball. She does not write Facebook posts about being terrified when a member of her family is pulled over by the police. She does not Crip Walk in celebration of her victories, and her father doesn’t talk about his memories of lynching and Jim Crow.

If Serena is the boogeywoman who won’t let anyone forget about race at large and American blackness in particular, then Osaka has been branded, without her consent, as the angel who will deliver us from such sordid unpleasantries.

Make no mistake, though. Osaka sees herself as an agent of change.

That’s especially true in Japan, which, being composed of 98.5 percent ethnic Japanese, is deeply homogeneous. Her relationship with the country is complicated, in part because of her status as a hafu, the Japanese word for a person with one parent who is ethnically Japanese and one who is not.

“There’s never been a Japanese tennis player that’s like me,” Osaka says. “For me, one of the biggest things, I want people to be able to understand that you don’t have to look Japanese or even speak Japanese to be Japanese. If I have Japanese blood in my veins, how are you gonna—I don’t know. How do people categorize being a nationality? It’s something that I want people to think about, in a way.”

Osaka admires other famous hafu such as Apolo Anton Ohno, Jhene Aiko and Kimora Lee Simmons. She boasts millions in Japanese sponsorships. But she experienced her first global public relations hiccup in January, when one of those sponsors, the ramen company Nissin, released an anime commercial of her in which Osaka’s skin and hair appear lightened. Westerners accused the company of “whitewashing” Osaka. Nissin apologized and pulled the ad.

Still, though she lives and trains in South Florida, the decision to mount Osaka’s worldwide takeover as a Japanese national has paid off. Her pathbreaking accomplishments, like being the first Asian to be the No. 1-ranked tennis player in the world, are framed in terms of her Japanese ethnicity. Technically, Osaka is also the first Haitian woman to be ranked No. 1, but she does not compete as a Haitian national. In news stories, though, she wants both nationalities recognized. “I’m half of each, you know?

“The funniest thing is, after I win something or do well somewhere, people start talking about my nationality or my ethnicity as if that’s the biggest thing about me, which I guess is true because it’s one of the biggest things you notice first,” Osaka says. “And then people start saying I’m American ’cause I live in America or I’m Haitian because my dad is Haitian, I’m Japanese ’cause my mom’s Japanese. I don’t know, I’d rather they just focus on the tennis.”

One day after posing for photos with the Daphne Akhurst Memorial Cup on Brighton Beach, Osaka is standing at the ticket counter at the Melbourne airport with Bajin and her father, Leonard Francois. Bajin checks bag after bag of tennis gear and luggage. Osaka sports a slouchy gray shrug, yoga pants and the pair of aviator frames she frequently wears when she’s not using contacts. Her blond-highlighted curls poke out the back of a baseball cap. None of the other travelers notices that the No. 1 tennis player in the world is standing a few feet in front of them. This trip home is likely one of the last remaining moments of invisibility for Osaka.

But how much of herself will she share with the world? That’s up to her, and it might never be very much.

The night she won her second grand slam, Naomi called her mother when she finally had a free moment after several hours of interviews, celebrations and photo opportunities. Tamaki told Naomi to hang up and go to sleep. “I just want her to be happy,” Tamaki says. “Is my answer appropriate? I want her to be happy. … Good life. No worries. Learn something from people or what you do every day. Be a better person every day.”

Tamaki knows two straight grand slam trophies are likely just the beginning of a history-making career for her daughter. But like Naomi, Tamaki likes the idea of maintaining a little mystery.

“Say, for example, you have a beautiful diamond, like 5 carat,” Tamaki says. “You don’t want to wear it every day. You want to keep it secret. It’s that kind of feeling, like I don’t need people to know I have that.”

Liner Notes Still craving the spotlight? Check out our full list of the world’s 100 most famous athletes on ESPN.com March 12. Hair by Lennie Billy/Artists at Wilhelmina, Makeup by Nina Alcantara/Artists at Wilhelmina, Wardrobe by Erika Golcher.