The four-time Grand Slam winner lit the cauldron at the opening ceremony of the Tokyo Olympics on Friday and it was a choice that could be appreciated worldwide.

In Japan, of course, the country where Osaka was born and the nation that she plays for; in embattled Haiti because that's where her father is from; and surely in the United States, because that's where the globe's highest-earning female athlete lives and where she's been outspoken about racial injustice.

Plus, everywhere in between, because Osaka is a superstar.

Yet she's often received an uncomfortable welcome in Japan because of her race, with her family having moved to the US when she was three.

Her emergence as a top tennis player has challenged public attitudes about identity in a homogeneous culture that's being pushed to change.

It's always a mystery until the last moment who gets the honour of lighting the cauldron but there was an inevitability about the choice of Osaka.

She stood at the centre of the stage when a staircase emerged, the cauldron opened atop a peak inspired by Mount Fuji and she ascended with the Olympic and Japanese flags blowing in the breeze.

She dipped the flame in, the cauldron ignited and fireworks filled the sky.

"Undoubtedly the greatest athletic achievement and honour I will ever have in my life," Osaka wrote on Instagram.

"I have no words to describe the feelings I have right now, but I do know I am currently filled with gratefulness and thankfulness."

It capped a dramatic series of events over the past two months for the 23-year-old Osaka.

Going into the French Open in late May, Osaka, the world's No.2 player behind Australian Ash Barty, announced she wouldn't speak to reporters at the tournament, saying those interactions create doubts for her.

Then, after her first-round victory, she skipped the mandatory news conference.

Osaka was fined $15,000 and - surprisingly - publicly reprimanded by those in charge of grand slams, who said she could be suspended if she kept avoiding the media.

The next day, Osaka withdrew from Roland Garros entirely to take a mental health break, revealing she has dealt with depression. She sat out Wimbledon, too.

So the Tokyo Games mark her return to competition.

She was originally scheduled to play 52nd-ranked Zheng Saisai of China in the very first match of the Games on Saturday but, clearly, her late night duties meant she wouldn't have had enough rest for an early morning match so she'll now play Sunday.

Osaka is the first tennis player to light the cauldron and one of the few athletes to be given the honour while still competing.

She'll hope to emulate Australian Cathy Freeman, who launched the 2000 Sydney Games and went on to win gold in the 400 metres.

Australian Associated Press