Naomi Osaka advanced to the Australian Open women's singles final after defeating Serena Williams on Wednesday
Naomi Osaka and Mari Osaka
Credit: Aflo/Shutterstock

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.

"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.

Australian Open
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.

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.

Want to get the biggest stories from PEOPLE every weekday? Subscribe to our new podcast, PEOPLE Every Day, to get the essential celebrity, entertainment and human interest news stories Monday through Friday.

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.