Chella Choi rallied with three birdies down the stretch for a four-under 67 and a one-shot lead after the second round of the LPGA Tour's Jamie Farr Toledo Classic.
Choi, winless in her four years on the LPGA tour, on Friday recovered nicely after starting her back nine on a sour note with two straight bogeys.
She shot an opening round 66 and was at nine-under 133 to lead a Korean assault at the rainy Highland Meadows Golf Club.
Five of the top eight golfers were from South Korea.
Inbee Park had the low round, climbing 29 spots on the leaderboard with a six-under 65. Park is the winner of the tour's most recent tournament, the Evian Masters.
Japan's Mika Miyazato had a 68, and South Korea's Hee Kyung Seo a 66 to join Park at eight under.
First-round leader Pernilla Lindberg, South Korea's Hee-Won Han, Karine Icher of France and South Korea's So Yeon Ryu were another shot back. Lindberg had a 71, Han shot 67, Icher 69 and Ryu 68.