Top-seeded Samantha Stosur of Australia beat Erika Sema of Japan 6-4, 6-2 on Monday to advance to the second round of the Japan Open.
Stosur, who won this tournament in 2009, hit five aces and converted five of six break points to win in 1 hour, 16 minutes at Utsubo Tennis Center.
The ninth-ranked Stosur reached the semifinals of the Pan Pacific Open in Tokyo earlier this month and is seeking her first title of the year.
In other matches, Jamie Hampton of the United States overpowered Japan's Ayumi Morita 6-3, 6-2 while France's Pauline Parmentier beat compatriot Mathilde Johansson 6-2, 6-2 to also advance.
Casey Dellacqua of Australia beat Japanese veteran Kimiko Date-Krumm 6-3, 3-6, 6-4 while Britain's Heather Watson advanced after a 6-4, 6-4 win over Slovakia's Polona Hercog.
Japan's Misaki Doi also moved on to the second round, beating American Julia Cohen 7-5, 3-6, 6-0.