Japan's Naomi Osaka got off to a winning start in the Citi Open women's singles on Tuesday, posting a straight-sets victory over American Bernarda Pera in the first round.

The third-seeded Osaka, who is making her debut at the July 30 to Aug. 5 hardcourt tournament, prevailed 6-2, 7-6(4) in a rain-delayed match at Rock Creek Park Tennis Center in Washington.

The world No. 17 claimed the first break of the match in the sixth game with a backhand winner before breaking Pera's serve again to seal the first set.

Though playing with a taped right thigh, Osaka managed to pull off eight aces and won 71 percent of her points on her first serve. Pera, ranked 95th, struggled with eight double faults.

Osaka is playing in her first event since Wimbledon, the grass-court Grand Slam, where she lost her third-round match. But the 20-year-old said she is confident she can play in top form on her favorite surface.

(Bernarda Pera, left, and Naomi Osaka after their match)

"Hardcourt is like my home, so I feel really comfortable. I'm definitely looking forward to playing in the next round," said Osaka, who claimed her first WTA title at the hardcourt Indian Wells in March.

"I think I'm so used to hardcourt, like I grew up on hardcourt and I've played almost my whole life on hardcourt. I'm so comfortable on it as opposed to red clay or grass," she told Tennis Channel in a postgame interview.

Among other Japanese, Nao Hibino also advanced to the second round in the women's singles with a 7-5, 6-4 win over Russia's Sofya Zhuk.

In the men's draw, Yosuke Watanuki lost to Russian Daniil Medvedev 3-6, 7-5, 6-1. Following a suspension of play due to rain, Yuichi Sugita lost to France's Vincent Millot 6-3, 6-2.

Former world No. 4 Kei Nishikori, who received a first-round bye in the men's singles, will face American Donald Young in his tournament opener on Wednesday.