The two-times Grand Slam champion has faced a backlash on social media after throwing her support behind the Black Lives Matter (BLM) protests in the wake of the death of George Floyd, an unarmed black man who died in police custody on May 25.

The 22-year-old Osaka, who has Japanese and Haitian parents but grew up and lives mostly in the United States, says she has no intention of backing down and hopes to help drive real and permanent social change.

"I’m vocal because I believe in the movement and want to try to use my platform to facilitate change," Osaka told Reuters via email.

"George Floyd’s murder and the situation generally in America has had a big impact on me.

"Being silent is never the answer. Everyone should have a voice in the matter and use it."

The death of Floyd while he was in the custody of the Minneapolis police has sparked worldwide protests against racism and calls for reforms of US law enforcement.

Osaka said she had marched in Minneapolis and attended other Black Lives Matters protests in Los Angeles, where she lives.

She says the climate has changed considerably since quarterback Colin Kaepernick took a knee during the national anthem before a 2016 NFL game and paid for his protest by being ostracized by the league.

"Colin has been putting this message out since 2016. It took a pandemic, an economic crisis and a torturous murder on camera, all at the same time, for people to really hear him," she said.

"It shouldn't have been that way. If the NFL wants to show that they really care the first thing they should so is take a knee together and give Colin his job back.

"That some people have said we as athletes should stick to sports is really insulting."

National Football League Commissioner Roger Goodell said last week the league had made mistakes in not listening to players and encouraged them "to speak out and peacefully protest".

"Hateful and sad"

In response to her comments on social media, Osaka has been told to "stay in her lane" and focus on tennis but has chosen to respond to her critics with argument and a few amusing GIFs.

"I probably shouldn't read all the trolling but it's hard to avoid," said Osaka, who has over a million followers on Instagram.

“Using humor is definitely one mechanism to expose these people ... Calling them out for their ignorance and racism is also worthwhile sometimes.

"I’m more sad for them than myself – to be so hateful and ignorant can't be an easy way to live life."

Osaka said racism needed to be challenged all around the world and was delighted to see Black Live Matters protests in Japan, the country she represents on the international stage.

On Tuesday, Japanese public broadcaster NHK had to apologize for an animated video aimed at explaining the US protests which sparked outrage for its depiction of black Americans.

Osaka retweeted the video with a GIF expressing bewilderment.

"We have been trying for hundreds of years and a change is long overdue," she said.

"I do think this time there is a different feel and energy, and the protests are so far reaching. There have even been BLM marches in Japan! That makes me so happy.

"So I’m hopeful for change, I'll keep campaigning for change, and I demand a better future for the next generation."