Australian Open tennis: Naomi Osaka sends written message to sister about 'disturbing' group chat after beating Serena Williams

Naomi Osaka writes a massage on a TV screen after defeating Serena Williams. Photo / AP

Naomi Osaka's sister Mari has revealed the exact group chat post that earned her a lighthearted rebuke in front of the world on Wednesday.

Osaka put her sister on blast following her red-hot 6-3 6-4 win over Serena Williams and celebrated the big victory by signing a bizarre message aimed at her older sibling on the camera lens of one of the courtside broadcast cameras.

The three-time grand slam champion was all class in her post-match comments towards the ousted American champion, but also had time to embarrass her sister.

Osaka wrote on the lens: "Mari stop sending werid (sic) images in the groupchat!"

The message left the world wondering what was going on inside the Osaka family and the 23-year-old 2019 Australian Open champion spilt the beans in a post-match interview with Eurosport.

"She sends really weird images and apparently I spelled 'weird' wrong so my bad," she said.

"She sends really strange images in the group chat to me and my friends. Sometimes it's a bit disturbing but we love her either way."

Even before Osaka could turn her attention to a showdown with American Jennifer Brady in the women's final on Saturday night, her sister was stealing the limelight.

Having been inundated for the goss of exactly what Osaka was complaining about, Mari confessed to the accusations with an Instagram post on Thursday, which showed the image that made her younger sister less than comfortable.

Mari Osaka revealed what the 'disturbing' messages were. Photo / Instagram

Osaka will have more important things on her mind by the time Saturday rolls around.

Earlier, she shared a hug with Williams after their semi-final battle.

Osaka was full of admiration for her former idol.

"I was just really, like, nervous and scared I think in the beginning. Then I sort of eased my way into it," she said.

"It's always an honour to play her. I just didn't want to go out like really bad, so I just wanted to try my best.

"I don't know if there's any little kids out here today, but I was a little kid watching her play and just to be on the court playing against her for me is a dream."