The Japanese third seed fought back from a service break down in the second set before advancing with a 6-2 6-4 victory over rising young Czech Marie Bouzkova.

Playing for the first time since blowing match points in her Brisbane International semi-final against Karolina Pliskova two weeks ago, Osaka came out firing.

She took the opening set with two service breaks before Bouzkova, making her Open debut on Melbourne Park's biggest stage, began to find her groove.

The 21-year-old fashioned several break points before finally capitalising to charge ahead 4-2 in the second set.

Forced to raise her game, Osaka responded to reel off four straight games to take the match in one hour, 20 minutes.

"It's really tough to play someone you've never played in the first round of a grand slam," Osaka said.

"But I understand that I don't have to play perfect in the first round. It's more about building your level up and getting comfortable with yourself.

"That's one of the biggest things I have learned. Also, just like understanding that every match you play is probably going to be very difficult and being okay with that."

Despite being up against it in the second set, Osaka said she didn't feel any pressure opening centre-court proceedings as reigning champ.

"For me, it's really odd here. I just feel really happy," the 22-year-old said.

"I don't really have this mentality of I'm, like, defending now. It's really weird.

"But I'm very thankful for it, because I think if I did go into the match with that, I would have been tense."

It was the 2018 US Open champion's 18th win from her past 19 grand slam matches on hard courts and set up a second-round clash with China's Zheng Saisai.

Zheng, the world No.42, earlier beat Russian qualifier Anna Kalinskaya 6-3 6-2 in her opener.

"I played Saisai once a couple years ago, and she's a very tricky player. She slices and dropshots from what I could see of her matches in the past," Osaka said.

"It will be probably a match where I have to dictate a lot and just stay consistent and be positive. Because there are going to be times where I do think I'll be frustrated."

Australian Associated Press