Bo-Mee Lee fired an 8-under 64 Saturday and moved four strokes clear of the field after two rounds of the Mizuno Classic.
Lee, who is playing for the seventh time on the LPGA Tour, finished 36 holes at 10-under-par 134.
Rikako Morita carded a 4-under 68 to move into second place at minus-6 at Kintetsu Kashikojima Country Club.
Ayako Uehara, who shared the first-round lead with Jiyai Shin, shot 72 on Saturday and slid into a share of third at 4-under-par 140. Uehara was joined there by HSBC Women's Champions winner Angela Stanford (71), Karine Icher (69), U.S. Women's Open champ Na Yeon Choi (71) and Jenny Shin (69).
Jiyai Shin (73), Stacy Lewis (70) and women's world No. 1 Yani Tseng (70) headline a group of eight players tied for eighth at minus-3.
Lee was two strokes off the lead to start the round, but closed that gap with a birdie at the first. After four pars in a row, she flew into the lead.
The Korean birdied the sixth and seventh to lead by one. Lee converted a birdie effort at the ninth and followed with birdies at 10 and 11 to move to minus-8.
Lee parred her next two holes. She converted back-to-back birdie efforts at 14 and 15 to get to 10-under. Lee parred the final three holes to lead by four.
"When I started this week, I was thinking my game was nice," Lee stated. "I think the first and second rounds went great, so I'm ready for final round."
Morita, who is also playing her seventh LPGA Tour event, birdied the second to move to 3-under. She carded birdies at six and eight before making two pars around the turn.
At the 11th, Morita converted a birdie effort and made it two in a row with a birdie on No. 12. She made a 10-foot eagle putt on the par-5 13th to jump within one of the lead at minus-9.
However, Morita bogeyed three of the next four holes to fall four off the lead. That is where she ended after a par at the last.
"Lately, I've been missing some short putts, but today I didn't, so I'm pretty satisfied," said Morita. "I'm a little bit behind, but it's not too hard to make birdies on this course, so hopefully I can put some pressure on the leader tomorrow."
NOTES: Lee's best tour finish was a tie for 11th at the 2009 HanaBank - KOLON Championship ... Lee is a 4-time winner on the Korean LPGA and earned her first Japan LPGA Tour win earlier this year ... Morita's best finish was a share of 20th at last year's Evian Masters.