U.S. Open champion Naomi Osaka thrilled her Japanese fans with a display of power and precision at the Pan Pacific Open on Wednesday, dominating Slovakia's Dominika Cibulkova in a straight-sets victory.

The world No. 7 Osaka controlled every aspect of their second-round match, wrapping up the 6-2, 6-1 win in just under 60 minutes.

Making her first appearance since claiming her maiden Grand Slam, the 20-year-old Japanese was greeted with loud cheers from the sellout crowd at Arena Tachikawa Tachihi.

The third seed, who received a first-round bye, made a fast start, hitting an impressive forehand winner at the net to break the 30th-ranked Cibulkova's serve in the opening game.

Serving in the second game, Osaka sent down the first of several aces to go up 40-0 before closing out for a 2-0 lead.

After Osaka hit a powerful forehand winner to lead 0-15 in the third game, Cibulkova battled her way back to deuce. But Osaka gained the advantage with a fortunate bounce off the tape before going up another break with a cracking backhand winner.

Despite looking untroubled throughout the match, Osaka said her first career meeting with Cibulkova had been challenging.

"It was really difficult. She is such a great player," said Osaka, who delighted the audience by sprinkling her on-court interview with a few Japanese phrases.

Asked whether she thinks the affectionate nickname "Naomi-chan" is fitting for a Grand Slam winner, Osaka replied in Japanese, "I like (to be called) 'Naomi-chan'."

Cibulkova, who beat Japan's Nao Hibino in the opening round, finally held serve in the fifth game to bring the score to 4-1, then fought back from 0-30 to win the seventh game.

That was as close as the Slovakian would get, however, with Osaka serving three straight aces to close out the first set in 33 minutes.

Cibulkova started the second set in more positive fashion, serving a love game to go up 1-0. But Osaka served a pair of aces to quickly close out the following game before securing the break to go up 2-1.

Utilizing her footspeed and an imposing forehand return, Osaka took three break points from the set against her overmatched opponent.

"It wasn't a match I was proud of. I just couldn't find my rhythm. She was serving well. I felt I was in control of some rallies, but it was too hectic," Cibulkova said.

In the previous match in the main arena, Alison Riske of the United States upset former world No. 1 Garbine Muguruza in straight sets.

The 75th-ranked Riske won three break points in the opening set on her way to a 6-1, 6-2 victory over the Spaniard, now ranked 14.

French second seed Caroline Garcia earlier survived a tough three setter against Anastasia Pavlyuchenkova of Russia.

World No. 4 Garcia fought her way back from 5-3 down in the third set, winning four straight games to take the match 6-4, 2-6, 7-5.