Miyazato had two different stretches of three straight birdies during her round Friday, recording nine birdies in total against a single bogey. She enters the weekend at 10-under 134, one shot clear of reigning U.S. Women's Open champion Na Yeon Choi.
First-round co-leader Suzann Pettersen, looking for her second win in her last three starts, closed with birdies on two of her final three holes to fire a 1-under 71. She will begin Saturday among a group tied for third at 7 under, three shots behind Miyazato.
Sun Young Yoo, who shared the lead after the first round with Pettersen and So Yeon Ryu, made a charge up the leaderboard mid-way through her round Friday before being undone by the par-5 14th hole. There she carded a double-bogey 7, which was later turned into a triple-bogey 8 after rules officials determined that she had taken an improper drop, resulting in a one-stroke penalty. Despite the mishap, she currently sits at 7 under, tied for third alongside Pettersen, Brittany Lincicome and France's Karine Icher.
Having already clinched Rolex Player of the Year honors, Stacy Lewis shot an even-par 72 Friday to remain at 2-under for the week, 10 shots behind the leader. Meanwhile, Michelle Wie continued to struggle Friday, carding a 5-over 77. At 14-over 158 after two rounds, Wie remains in last place among the 73-player field.