Osaka had earned a wildcard spot in the women’s singles main draw after not ranking high enough to qualify directly. She entered the tournament with an 18-15 record and ranked 88th in the world.

After most recently losing in the qualifying rounds of the Cincinnati Open, Osaka opened up in a post on Instagram about the mental struggles she faced since giving birth to her first child.

“I don’t feel like I’m in my body,” Osaka wrote at the time. She signed off her message with a promise to give it her best shot as she headed for New York.

So far, her hard work seems to have paid off.

Osaka has won the U.S. Open twice, including in a controversial match against Serena Williams in 2018. In her last appearance at the tournament in 2022, Osaka lost to American Danielle Collins in the first round.

When addressing the crowd, Osaka also said that she had to hold her daughter for awhile the night before after she couldn’t fall asleep. Despite the inconvenient timing, Osaka said the moment was special.

“Moments like that are really precious to me and I can only hope to keep having more,” she said.

The first round of the U.S. Open also saw hype around 16-year-old Iva Jokic, who pulled off a stunning upset as the youngest American to win a women’s main-draw match at the U.S. Open since 2000.

Osaka will next face Karolina Muchova in the second round on Thursday.