The tennis superstar Naomi Osaka has hit back at those who criticized her decision to represent Japan instead of the United States at this summer's Olympics, saying that her plan to play for the Asian nation shouldn't have been a surprise to commentators.

"I've been playing under the Japan flag since I was 14. It was never even a secret that I'm going to play for Japan for the Olympics," she said while discussing the backlash during an episode of her new self-titled docuseries on

"So I don't choose America and suddenly people are like, 'Your Black card is revoked.' And it's like, African American isn't the only Black, you know? I don't know, I feel like people really don't know the difference between nationality and race because there's a lot of Black people in Brazil, but they're Brazilian."

Osaka announced that she would be relinquishing her American citizenship in 2019. The tennis star who was born in Japan but moved to New York at the age of 3 previously held dual American and Japanese citizenship. But under Japan's Nationality Act, those who hold dual citizenship must choose one before their 22nd birthday.

Osaka's mother is Japanese, and her father is Haitian.

At the time, Osaka told the Japanese broadcaster NHK that she had a "special desire" to represent her birth country at the Olympic Games.

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

In 2018, Osaka's mother, Tamaki, told The Wall Street Journal that her daughter has deep cultural ties to Japan and made the decision to represent her country of birth early in her career.

"We made the decision that Naomi would represent Japan at an early age," her parents told the publication.

"She was born in Osaka and was brought up in a household of Japanese and Haitian culture. 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."

Earlier this year, the 23-year-old — who is the first Asian player to reach the No. 1 world ranking and the highest-paid female athlete in the world — withdrew from both the French Open and Wimbledon. In an essay for Time magazine, Osaka explained that she'd decided to step away from the game to take care of her mental health.

But later in the essay, Osaka confirmed that she would return to the court to represent Japan at the Olympics, which are being held in Tokyo.

She said: "After taking the past few weeks to recharge and spend time with my loved ones, I have had the time to reflect, but also to look forward. I could not be more excited to play in Tokyo. An Olympic Games itself is special, but to have the opportunity to play in front of the Japanese fans is a dream come true. I hope I can make them proud."