Japan's Shiho Oyama upstaged the US LPGA Tour regulars by firing a 4-under 68 to take a one-stroke lead after the first round of the $1.2 million Mizuno Classic Friday.
Oyama, a 12-time winner on the Japan LPGA Tour but winless since 2011, overcame a sore neck to card six birdies and two bogeys on the par-72 Kintetsu Kashikojima Country Club course in Shima, central Japan.
"I'm just glad I could make it around the course without any problems," said Oyama, who underwent massage and acupuncture to overcome the intense pain. "It's a miracle that I recovered."
Defending champion Stacy Lewis of the United States, the highest-ranked player in the tournament at No. 3, could only manage two birdies against one bogey and was three shots back in a large group tied for 20th place.
The tournament, which offers a top prize of $180,000, is the final event on the US LPGA Tour's Asian swing. It is co-sanctioned by the US and Japan tours.
Two-time former champion Shin Ji-Yai was among five South Koreans in a nine-way tie for second place, along with American Brittany Lincicome and Sweden's Pernilla Lindberg.
Also at 3-under 69 were South Korea's Lee Na Ri, who has won twice over the past two months on the Japan LPGA Tour, Choi Chella, Han Hee-Won and Jang Eun-Bi. Others in the group are Japan's Kaori Nakamura and Junko Omote.
Americans Austin Ernst, Brittany Lang and Danielle Kang were another shot back in a group of nine at 2 under.
The 36-year-old Oyama, who has been limited to 18 tournaments due to a groin injury, had the first-round lead twice before this season in Japan, but ended up finishing third at the Axa Ladies and tied for fourth at the Chukyo TV Bridgestone Ladies. She has finished in the top-10 six times and has made every cut.
Unable to fully swing the club without pain the day before, Oyama said she felt fine during the round.
"When I played before with Brittany, she left me far behind [off the tee]," Oyama said. "Today, there was no difference between us in distance."
Lewis, looking for her fourth title of the year, was in good company at 1 under, with that group including Japanese star Mika Miyazato, South Korean world No. 4 Ryu So Yeon and Scotland's Catriona Matthew.
Lewis has finished no worse than seventh in eight of her last nine starts. The lone black mark came when she withdrew from the CN Canadian Women's Open after falling ill during the first round.
Miyazato, who last year became the 11th Japanese player to win on the US LPGA Tour, made a successful return last month to Japan. In a rare appearance on the domestic tour, she captured the Japan Women's Open.