OSAKA, JAPAN (AP) - Top-seeded Naomi Osaka reached the quarter-finals at the Pan Pacific Open by beating Bulgarian qualifier Viktoriya Tomova 7-5, 6-3 on Wednesday (Sept 18).

The 21-year-old, who was broken twice early in the match, is looking to win her first title in her home town after finishing runner-up in 2016 and 2018.

She will next meet either Kazakh Yulia Putintseva or Russian qualifier Varvara Flink.

Also, fourth-seeded Angelique Kerber won her first match since Wimbledon, beating American qualifier Nicole Gibbs 6-2, 6-4.

"The goal now is to finish the year as well as I can, to put all the energy which I have into this run in Asia and to play well in the next few weeks," the 31-year-old German said.

Kerber will next face American Madison Keys, who defeated Zarina Diyas 5-7, 6-0, 6-4.

"I know Madison really well, so I know what to expect," the three-time Grand Slam champion said. "It will be interesting. We both know we have to play our best against each other."

Belgium's Elise Mertens also advanced, beating Chinese Taipei's Hsieh Su-wei 6-3, 1-6, 6-2 win.

At the Korea Open in Seoul, second-seeded Ekaterina Alexandrova recovered well to beat Kristyna Pliskova 3-6, 6-3, 6-4 and reach the quarter-finals.

The Russian will next play Kristie Ahn. The American advanced by beating Ana Bogdan of Romania 0-6, 6-4, 7-6 (7-2).

Magda Linette also made the last eight, defeating Anastasia Potapova 7-5, 7-6 (7-4). The fourth-seeded Pole will next meet Kirsten Flipkens, who upset seventh-seed Margarita Gasparyan 6-3, 7-5.