MELBOURNE, Australia — The most uncomfortable moment for Naomi Osaka on Saturday night was not when she faced a key break point in the first set of her Australian Open women’s singles final against Jennifer Brady. Nor was it when she was serving for the match in the second.

It came two hours after she closed out her 6-4, 6-3 victory at Rod Laver Arena. At the start of her news conference, Craig Tiley, the head of Tennis Australia, handed Osaka a flute of champagne and proposed a toast to her second Australian Open crown and fourth Grand Slam title.

Osaka, 23, brought the glass to her lips and tentatively took a sip, trying unsuccessfully to keep her expression neutral. She has never developed a taste for alcohol, she had explained earlier in the tournament, because she was told as a child that it was bad for her.

“Like it’s ruining your body or your liver,” she said. “I just want to give myself an advantage for as long as I can.”

Osaka, the pride of Japan who spent much of her childhood in Florida, would appear to have a leg up on the rest of her competition in an increasingly deep women’s game. She is 4 for 4 in Grand Slam finals, a feat achieved in the Open era only by Monica Seles on her way to nine total championships and Roger Federer on his way to 20.

“That’s very amazing company,” said Osaka, who held her childhood idol, the 23-time Grand Slam champion Serena Williams, to the same number of games, seven, mustered by Brady, a 25-year-old in her first major final.

She added, “You can only just keeping going down your own path.”

Osaka, who won her second United States Open title this past September, is halfway to a Naomi Slam. She is unbeaten in her past 21 matches. Her most recent loss in an individual competition came in the third round of this tournament last year when she was upset by the United States teenager Coco Gauff, a defeat that weighed on Osaka’s mind before she took the court against Brady who was the decided underdog like Gauff had been.

“I have been in the position that she is in to go into the first Slam,” Osaka said, referring to Brady. “Of course I know the nerves that come with that. But then I was thinking on the other side, for me, I wonder if I’m expected to do better because I have been in Slam finals before. So there was actually a lot of nerves with that.”

Both players looked nervous in the early going, missing first serves and racking up roughly two unforced errors for every winner. With Osaka serving at 4-4 in the first set, Brady chipped away at Osaka’s fortress until she had opened a sliver of daylight at 30-40.

On break point, Osaka missed her first serve, directed a second attempt at Brady’s body and then took the point with a forehand winner, one of four she’d record in the match. She won the next two points to seal the opening shut.

Brady took a 40-15 lead on her serve in the next game, only to be reeled in by Osaka, who broke her when Brady netted a short forehand — an error, she bemoaned, “that happens maybe one in ten times or hopefully less.”

For Osaka, the uncharacteristic miss telegraphed Brady’s unease.

“My mind just began thinking that she was either really nervous or really pressured and I should capitalize on that by trying to win as many games as I could, pace-wise,” Osaka said. “Because I feel like once a person loses the first set doubts start to creep in, so that’s when you really should put your foot on the gas.”

Nobody in the game right now is a better pacesetter than Osaka, who improved to 45-1 in Grand Slam matches when she wins the first set. She raced to a 4-0 lead in the second, needing 36 minutes to close out the match.

“She played really well when she had to,” Brady conceded. “She hit good shots when she needed them.”

Osaka, who also won the 2019 Australian Open, called it a privilege to be able to play a major tournament given the coronavirus pandemic. “I didn’t play my last Grand Slam with fans, so just to have this energy it really means a lot,” she said, referring to her three-set victory over Victoria Azarenka in New York.

Brady, a 25-year-old American, lost to Osaka in a hard-fought semifinal at the U.S. Open. A member of U.C.L.A.’s 2014 national championship team, Brady became the first woman with collegiate experience in this tournament’s final since 1983. She was trying to become the first to win the title since Barbara Jordan of Stanford did so in 1979.

Brady, who was outside the top 50 at the start of 2020, entered the tournament ranked 24th in the world, and after her run at Melbourne Park, she will vault to No. 13.

The third-ranked Osaka will move to No. 2, behind the Australian Ashleigh Barty, who fell in the quarterfinals. Osaka, who spent long stretches of 2019 at No. 1, said she is not fixated on regaining the top spot.

“I feel like I’m at a really good place right now,” Osaka said. “I just want to play every match as hard as I can. If it comes to the point were I’m able to be No. 1 again, I’ll embrace it, but I’m not really chasing it.”

Osaka’s path to the final in Melbourne included a close call with defeat in the fourth round, where she faced Garbiñe Muguruza and staved off two match points in a 6-4, 4-6, 7-5 victory. She dropped just 18 games in her final three matches.

Among active players, only two women have more Grand Slam titles than Osaka: Williams and her sister Venus, with seven. Osaka’s championships have all come on hardcourts, starting with her victory at the 2018 U.S. Open, where she beat Serena Williams in straight sets in the final. Osaka said the one of her goals this season is to expand her success to other surfaces, starting with clay since the French Open is the next scheduled Grand Slam.

“I don’t expect to win all my matches this year,” Osaka said, adding, “I don’t think it’s possible. Tennis players, we go through ups and downs. But for me, I only hope that my ups and downs are less drastic this year.”

Osaka’s long-term objective, she said, is to last long enough in tennis to someday face an opponent whom she inspired to take up the sport.

“For me, that’s the coolest thing that could ever happen to me,” she said.