NEW YORK — Newly minted U.S. Open semifinalist Naomi Osaka grew up on Long Island until she was 9, but tennis fans wouldn’t be able to tell that by simply watching her on the court. The flag next to her name displayed on monitors throughout Billie Jean King National Tennis Center is Japan’s — her mother’s homeland, the country of her birth and the country she represents in competition.

On her days off, though, she enjoys the city like a New Yorker.

“Well, in the mornings I don’t play matches, I walk around and hear the lovely honking,” Osaka said. “I just like walking in the city. It’s just there’s a lot of energy — and then you come back to the hotel very angry because everyone just makes you angry . . . like, ‘Oh, why are these people walking so slow?’ ”

Osaka defeated Lesia Tsurenko on Wednesday, 6-1, 6-1, to advance to her first career Grand Slam semifinal.

For Osaka, her victory is the latest milestone in a watershed year for the 20-year-old who won her first WTA Tour title in Indian Wells, Calif., in March. Osaka, like many her age, is a power hitter. But her killer instinct sets her apart.

She dropped only seven points on her serve playing on Arthur Ashe Stadium and needed just 57 minutes to rip through Tsurenko. In her third-round match, she was even quicker, dominating Aliaksandra Sasnovich, 6-0, 6-0, in 50 minutes.

Osaka earned a semifinal date against reigning runner-up Madison Keys on the biggest stage of her career after Keys defeated Carla Suarez Navarro, 6-4, 6-3. Osaka said she has tried to keep this tournament business-like as she navigates her way through the draw, but her triumph in New York is not just about advancing her career. It’s personal.

Osaka, whose father is Haitian, is the first Japanese woman since the start of the Open era to reach the U.S. Open semifinals and the first to reach any Grand Slam semifinal since Kimiko Date did it in 1996 at Wimbledon. A short while after her win, Kei Nishikori held off Marin Cilic in five sets to mark the first time in the Open era that a Japanese man and woman advanced to the semifinals at the same Grand Slam.

To win a title or even make a final in New York, where she and her sister Mari grew up learning tennis in a Haitian household with her father’s parents and eating her mother’s Japanese food, would speak to every part of Osaka’s multicultural experience.

“New York is very nostalgic. I used to play here when I was a little kid, so these courts aren’t new to me,” Osaka said. “. . . It definitely means a lot, and I always thought if I were to win a Grand Slam, the first one I’d want to win is the U.S. Open because I’ve grown up here, and then my grandparents can come and watch. It would be really cool.”

As Osaka has climbed the ranks in women’s tennis, her identity has been the subject of curiosity for many tennis fans.

Long identified as a promising up-and-comer with power that causes Chris Evert to compare her to Serena Williams, Osaka has been asked about her background at every step of her career. In the spring, that attention intensified when she beat three former world No. 1 players in Maria Sharapova, Karolina Pliskova and Simona Halep en route to her title in Indian Wells. At the following tournament in Miami, she beat Williams, her idol, with Williams’s former longtime hitting partner Sascha Bajin as her coach.

In New York, members of the Japanese media fill her news conferences after every match.

“I don’t really feel pressure from them,” Osaka said. “I feel a lot of support, and I’m really grateful about that.”

Osaka, who lived in her native Japan until she was 3, started playing tennis in New York after her father saw the Williams sisters playing at the French Open in 1999 and decided to teach his daughters. She is now based in Florida, trains with Bajin at Evert’s academy in Boca Raton, and made the decision to play for Japan largely because of financial reasons — the Japanese federation offered more support money than the U.S. Tennis Association.

Osaka proudly represents Japan on the court, but that financial decision was separate from her multicultural identity. She comes from three cultures, has dual citizenship with Japan and the United States and calls America home.

Her news conferences are bilingual: English-speaking press go first, then Japanese reporters ask questions in Japanese. She listens and understands but answers in English so she can give fuller, more nuanced responses.

“Japanese culture? I love everything about it. . . . America, I live here. I train in Florida. . . . And Haiti, if you’ve ever met a Haitian person, they are really positive, and literally if you’re friends with them, then they will do anything for you. That’s something that is a really good trait, and I’m really happy that my grandparents and my dad’s side of the family is like that,” Osaka said.

Though Osaka can be shy or sarcastic in front of the media, on tennis’s biggest stages she operates with confidence.

Her title in Indian Wells came against a fellow up-and-comer, Daria Kasatkina, and though Osaka is prone to errors, she came alive under the pressure. Her power and shot-making abilities were on display, as were her movement and positive on-court attitude that she has been working on with Bajin.

That penchant to perform in big moments makes her coach feel better about Osaka’s relative lack of experience as she moves deeper into the U.S. Open. Keys, 23, is a three-time Grand Slam semifinalist and Olympian.

“I believe that Naomi is one of those individuals who really craves the big stage, so that definitely helps her competing out there and helps my part, too, you know?” Bajin said. “She always plays better on the big stages than she does on any of the other courts.”