Why Naomi Osaka’s sister retired at 24 despite beating her ‘a million’ times as a junior

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Naomi Osaka has had a hall-of-fame career, reaching world number one and winning several Grand Slam titles.

Breaking through in 2018, Osaka defeated Serena Williams in the final of the US Open to secure the first of her four major titles.

Adding a second to her tally in Melbourne a few months later, Osaka rose to number one in the WTA rankings as a result.

Picking up her third and fourth titles over the next two years (US Open 2020, Australian Open 2021), Osaka became one of the most successful ‘active’ players in the women’s game.

However, what many fans don’t know is that there was once another Osaka working her way up the rankings…

Mari Osaka beat Naomi Osaka ‘a million’ times as a junior, but retired at 24 without a WTA Tour win

Osaka’s sister, Mari Osaka, turned professional in 2014 before retiring from tennis seven years later without ever recording a main draw win.

In a now-deleted Instagram post, Osaka explained her decision to retire from the game in 2021.

“I am retired from playing tennis,” she said.

“It was a journey which I didn’t enjoy ultimately, but I’m grateful for all the memories and support I’ve gained and received from the sport over the years.

“I’m moving on now, so you can look forward to new fun projects upcoming in the future.”

Never quite able to make the step up to elite competition, Osaka enjoyed her best results at the ITF [International Tennis Federation] level, where she reached four finals.

Her struggles may have come as a surprise to her younger sister, who revealed in a 2019 interview with the New York Times just how good Mari Osaka was when they were juniors.

“Up until I was 15, she was 6-0-ing me, ridiculous,” she said.

“I don’t know what happened, maybe finally something clicked in my head, but for sure she was beating me.

“In the win-loss record, she’s up by like a million or something.”

Never able to realize the potential she once showed, Osaka retired aged 24, having reached a career-high ranking of 280th in the world.

Since retiring, Osaka has focused her efforts on fashion and has collaborated with her sister on several projects.

How did Naomi Osaka and Mari Osaka fare when they played doubles together?

The Osaka sisters may be collaborating on fashion projects in 2025, but that’s not the first time they’ve worked together.

Back in 2017, Naomi Osaka and Mari Osaka received a wild card into the Pan Pacific Open doubles tournament.

Searching for their first title together, the sisters took on Makoto Ninomiya and Renata Voracova in round one.

Failing in their bid to reach the quarterfinals, the Osakas lost 5-7, 4-6, in their opening match.

They had previously played together at the ITF level, but only ever won one match as a duo.

In fact, Naomi Osaka has only won two career matches in doubles, the first alongside her sister in 2012, and the second with Misaki Doi in Strasbourg four years later.

The Japanese star has played just one doubles match since 2017, partnering Ons Jabeur to a first-round defeat in Abu Dhabi last year.

Only time will tell if we will see Osaka make a return to the discipline in the future, but the likelihood is that she will stick to singles.

Osaka will return to singles action on Tuesday, August 26, to play Greet Minnen in round one of the 2025 US Open.