South Korea's Lee6 Jeong-eun fired a bogey-free nine-under par 63 to grab a one-stroke lead after Friday's second round of the LPGA Queen City Championship.
World number 43 Lee6 birdied six of the first 10 holes in her low round of the season to stand on 13-under 131 after 36 holes at Kenwood Country Club in Cincinnati, Ohio.
"It was a good, bogey-free round," Lee6 said. "It has been a while (since) I played bogey-free so I'm really satisfied with my game. Two more rounds, so I'm going to focus just on what I'm doing."
China's Lin Xiyu was second on 132 with American Ally Ewing third on 133 and Australian Sarah Kemp and Mexico's Maria Fassi sharing fourth on 134.
Lee6, 26, won her only major and LPGA title at the 2019 US Women's Open, the same year she collected the LPGA Rookie of the Year award. She was also a runner-up at last year's Evian Championship.
Swing work has been a major part of Lee6's preparation.
"I'm fixing my swing these days. I focused on my downswing. That's why I finished strong," Lee6 said.
"I'm still not comfortable with my swing but it's getting better. I'm struggling (with) my swing but I gained confidence a lot from today."
Lee6 birdied the par-5 second and par-4 fifth holes, then reeled off four birdies in a row starting at the par-4 seventh. She added birdies at the par-5 12th and par-3 14th and a final birdie putt from 20 feet at the par-4 16th.
Playing partner Lin, the 18-hole leader after an opening 64, birdied the first and last holes with birdies at the seventh and par-5 12th in a bogey-free 68.
"All I'm doing is trying to catch Six," Lin said. "It was nice to play with her. We definitely helped each other out a little bit, staying aggressive.
"I feel like I hit it even better than yesterday. For the putts it (was) just little lip out here and there."
Lin, making her 188th career LPGA start, seeks her first tour title. She had her best LPGA finish in March at Thailand, when she lost a playoff to Denmark's Nanna Koerstz Madsen.
"It's easier to be only one behind than a couple behind," Lin said. "I wanted to have a little breakthrough this year, so I think the more times I got to knock on the door the better."
Ewing made six birdies in a row starting at the second hole but a closing bogey dropped her two adrift on 64 while Fassi birdied five of the last six holes to fire a bogey-free 66.
"I've been able to have some shorter stuff into the greens and been able to take on some pins," Fassi said. "As soon as I saw a couple of the putts go in, you just get a little more confident and the hole gets a little bit bigger."