Number three seed Elise Mertens booked her place in the second round of the Japan Open with a straight-sets win over Evgeniya Rodina.
The Belgian - who is 41st in the latest WTA rankings released on Monday following the US Open, where she was beaten in the opening round by eventual runner-up Madison Keys - came through 7-6 (8/6) 6-1 in just over an hour-and-a-half against Russian Rodina.
Fourth seed Kristyna Pliskova of the Czech Republic also progressed after her 7-5 7-5 win over Chang Kai-chen of Chinese Taipei, while Alison Riske, the seventh seed, came from behind to defeat fellow American Madison Brengle 5-7 6-3 6-4.
Elsewhere, there were also first-round wins for Chinese pair Qiang Wang and Xinyun Han, who knocked out home player Misa Eguchi 7-5 6-2 .
Slovakian Jana Cepelova went through to the second round after Aliaksandra Sasnovich of Belarus retired, having lost the opening set 6-3 and 1-0 down at the start of the second.