Mayu Hattori and Sakura Yokomine each shot a 6-under-par 66 on Saturday to pull into a three-way tie with Ahn Sun Ju after two rounds of the Earth Mondahmin Cup.
Ahn, the overnight leader after a first-round 64, fell back to earth with a 3-under par 69 for a two-day total of 11-under-par 133 at the Camellia Hills Country Club.
Chie Arimura (66) and Shiho Toyonaga (67) were at 10 under in a tie for fourth, while Megumi Kido (67) was one stroke further back.
Hattori and Yokomine each carded six birdies without a bogey on a day in which all but 25 of the 106 players on the course shot par or better. Ahn had the only bogey among the top three.
"I sank all the putts that were within my range," Yokomine said. "The key to that was being able to maintain my concentration on the greens."
"The mistakes I did make today were not very costly."
Ahn, however, said fatigue took its toll in the second round following her torrid start.
"I barely slept last night, woke up early and was extremely tired," said the 2011 tour money winner. "I'm not satisfied with shooting 3-under but it was an OK round."