Ayaka Watanabe shot a 5-under-par 67 to take the lead after the first round of the Cyber Agent Ladies on Friday.
The 20-year-old, who scored her first career victory in dramatic fashion at the Axa Ladies in March, drained six birdies through 14 holes and rebounded from bogeys on Nos. 16 and 17 with a final-hole birdie at Tsurumai Country Club.
Watanabe has a one-stroke lead over high school senior Haruka Morita, Yuki Ichinose and Mami Fukuda.
Defending champion Sakura Yokomine struggled to a 74 and teenage amateur Minami Katsu, who at 15 became the youngest ever winner on the Japan LPGA Tour when she captured the Vantelin Ladies Open last month, had a 76.
Last week's Fujisankei Ladies Classic winner, Phoebe Yao of Taiwan, is sitting out the ¥70 million event.
Matsumura, Kim atop leaderboard
Togo Aichi Pref. KYODO
Michio Matsumura stayed on course to defend his title at The Crowns on Friday, despite stumbling to a 1-over-par 71 in the second round.
Matsumura, who started the day with a four-shot cushion after a blistering round of 60 on Thursday, made a birdie-birdie start at the par-70 Wago Course.
But he struggled with three bogeys over his last five holes, and was joined at the top of the leaderboard by South Korea's Kim Hyung-sung at 9-under 131.
Matsumura won the Indonesia PGA Championship that opened the season for both the Japanese and Asian tours in March.
Kim, starting the day in a share of second, shot a 67 and was followed a stroke back in third place by compatriot I.J. Jang (68).
Ryo Ishikawa, who won this tournament in 2010 with a final-round 58, which at the time was the lowest 18-hole score of a sanctioned tour, shot a 68 and was tied for fourth with Tomohiro Kondo and Hiroshi Iwata at 6 under.
