South Korea's Jiyai Shin shot a 7-under-par 65 to share the lead with Japan's Yukari Baba after Friday's first round of the Mizuno Classic.
Shin, No. 1 in the LPGA rankings, got off to a strong start with five birdies on the front nine - including the first four holes at the Kintetsu Kashikojima Country Club.
Shin, who won here in 2008, had two bogeys after the turn but added four more birdies to pull even with Baba.
American Morgan Pressel was a stroke back at 6-under, offsetting a lone bogey with seven birdies, including one on the 18th.
South Korea's Na Yeon Choi, who successfully defended her title in the LPGA Hana Bank Championship in Korea last week, was tied for fourth with five others after a 67.
Japan's Ai Miyazato, who has won five times on the LPGA tour this season, struggled with her game and shot an even-par 72.
Miyazato is vying to become the first player from Japan to capture Player of the Year honors since Ayako Okamoto in 1987. She currently sits second in the race, two points behind leader Yani Tseng.
The $1.2 Mizuno Classic is the LPGA's lone tournament in Japan.
