The best score in the second round belonged to the Danish pair of Nicole Broch Estrup and Olympics-bound Nanna Koertz Madsen, who birdied their last two holes for a 60.
Ally Ewing and Jennifer Kupcho of the US had a 64, the same score they had in foursomes during the opening round.
The Thailand tandem of Jaravee Boonchant and Chanettee Wannasaen also had a 64, while the Taiwan duo of Ssu-chia Cheng and Wei-Ling Hsu had a 63.
The five leading pairs were at 12-under 128, leading to a wide-open weekend at Midland Country Club in the LPGA Tour's only official team event.
Three other teams, including Charley Hull and Georgia Hall of England, were one shot behind. Lexi Thompson and Brooke Henderson were among those two behind.
Auston Kim could not remember the par 3 where she and her 23-year-old Australian teammate made a bogey - rare for the fourballs format - but there was no forgetting the par-3 seventh. They were only one under for the round at the time, and Auston Kim hit first to 20 feet.
Grace Kim felt enough wind that she went up one club to a three-quarter 7-iron, and it looked good all the way.
"Was obviously just trying to put it close. All I see is it kind of disappear. I've had a lot of close shades, and this is actually my first one. So very exciting," Grace Kim said.
They birdied the next hole, and then had five birdies on the back nine, which did not include the lone par 5 on the back.
"A lot of good came from that hole, courtesy of Grace," Auston Kim said. "It felt really positive going forward from there."
The Danes played late in the afternoon and had a 10-shot deficit to make up when they got started. Koertz Madsen had an eagle on the par-5 third hole, and the duo surged into a share of the lead with birdies on the 17th and the par-3 closing hole.
Ewing and Kupcho had three birdies in their opening four holes, picked up three more birdies on the back nine and were never in serious trouble throughout the day.
"Jen played really solid," Ewing said. "We had a lot of good looks, which when you're playing best ball like that, if you both have birdie putts, that's really big. And she made several birdies today. It was good to see another good score, especially in best ball."
Cheng and Hsu picked up a bonus shot when Cheng holed out for eagle on the par-4 12th.
"Definitely pumped us up a lot," Cheng said. "I liked the approach number, and I tried to be out there and have a good tempo and put a good swing on it, and it went in. We were just really happy."
Perth's Hira Naveed and her Paraguayan playing partner Sofia Garcia made the seven-under cut on the line.
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