Hana Wakimoto of Japan shot a bogey-free 9-under 63 on Thursday to lead by two shots after the first round of the LPGA's Toto Classic.
Jin Young Ko of South Korea was two off the pace after a 65 at Seta Golf Course. Four players carded 66s to be within three shots of Wakimoto: Linn Grant, Ayaka Furue, Hyo Joo Kim and Jenny Shin.
Wakimoto's score tied the Seta course record. She hit 15 of 18 fairways and recorded her ninth birdie on her final hole to cap the best round of her career.
"Recently my ball striking has been very good, so I have been confident and I could attack the pins today," said Wakimoto, who is leading the field in birdies made (9) and is tied for the fewest putts through the first round.
Ko made one birdie during her first nine holes before sinking six more to put herself into contention.
"I didn't do anything on the front nine," Ko said after her bogey-free round. "Yeah, I played really nice on the back nine. I do not know what happened, but I really tried my best and I just want to keep myself. It's been a while since I played good score this year, so I am so happy."
Australian Minjee Lee was tied for seventh after a 67, and Canadian Brooke Henderson shot 70. Only eight players in the 78-player, no-cut field, were over par after the first round.
The Associated Press and Field Level Media contributed to this report.