Naomi Osaka Teases Sister Mari on TV for Being 'Weird' After Australian Open Semifinals Win

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Naomi Osaka knows that there's no better place to tease your sibling than on national television.

Following her major triumph over Serena Williams in the Australian Open women's singles semifinals Wednesday, Naomi surprised fans with an interesting message to her sister Mari, 24, as she left the court.

After sharing a hug with Williams, Naomi walked over to the camera to write a note on the lens for the viewers at home. Instead of writing something about the match, the 23-year-old used the opportunity to call out her older sister for her "weird" text messages.

"Mari, stop sending weird images in the groupchat!" the athlete wrote.

Mari, who is also a tennis player, later gave people a glimpse of the mysterious group chat messages on her Instagram Story.

RELATED: Naomi Osaka Defeats Serena Williams in the Australian Open Semifinals

"To the people asking what I sent in the gc," she wrote in a since-deleted post captured by USA Today. Mari then posted a photo of a person licking someone's eyeball.

Naomi beat Williams in straight sets 6-3, 6-3, 6-4 on Wednesday.

Naomi Osaka

She will now play in the Australian Open women's singles final on Saturday at Rod Laver Arena in Melbourne.

The Japanese tennis star last won the Australian Open in 2019, while Williams, 39, was victorious last in 2017, her seventh title at the Grand Slam tournament.

RELATED: Serena Williams Emotionally Leaves Australian Open Press Conference After Loss: 'Not an Ideal Outcome'

Naomi and Williams have played each other several times before in tournaments. Naomi won over Williams in the first round of the 2018 Miami Open, and then beat the mom of one in the women's singles final of the 2018 U.S. Open. But Williams struck back when she beat Naomi at the 2019 Rogers Cup.

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Naomi's big win over Williams at the 2018 U.S. Open is memorable to many but the match was also marred by a verbal altercation between Williams and chair umpire Carlos Ramos. Williams was given three separate on-court violations and later suggested that the umpire's actions were motivated by sexism.

Tune into the Tennis Channel to watch the match, and for daily coverage of the tournament.