Yuko Mitsuka shot a 6-under-par 66 to surge into sole possession of the lead after the second round of the Daikin Orchid Ladies on Saturday.
Mitsuka, who won her second career title on the Japan LPGA at last year's Nichirei PGM Ladies, drained six birdies, including three in a row after making the turn en route to moving to 8-under 136 at the season-opening event at Ryukyu Golf Club.
The 24-year-old Ibaraki native shrugged off driving rain in a blemish-free round to move two shots clear of Ayako Uehara, who shot her second straight 69, while Australian Tamie Durdin (71) was alone in third on 140.
Erina Hara (71) followed in fourth and 15-year-old amateur Makiko Higa (69) was six strokes off the leader in a group of six players tied for fifth at 142.
Overnight co-leader Sakura Yokomine lost ground with a 75 following an opening-round 68 and slipped into a tie for 11th in a group featuring last year's money title winner Miho Koga on 143.
Defending champion Song Bo Bae of South Korea, who shared the opening-round lead with Yokomine, faltered with a 76 to drop into a tie for 16th.