Se Ri Pak posted a round of 65 to join Jung Yeon Lee in a tie for second at 12-under-par 132. Grace Park, Rachel Teske and Yuri Fudoh were one shot further back at 11-under-par 133.
Sorenstam began her quest to win this event for the third consecutive year with a remarkable opening round and wasted little time on Saturday with a birdie at the very first hole at Seta Golf Course.
She added a birdie at the third and picked up back-to-back birdies from the par-3 fifth to move to 13 under. Sorenstam then birdied the par-4 eighth to begin to pull away from the pack.
Sorenstam continued her fine play on the inward half and ran off two consecutive birdies starting at the par-4 10th.
The 34-year-old then closed her round in style with birdies on each of the last two holes to match the course record she had established the day before.
Sorenstam's total of 126 was two strokes off the all-time 36-hole scoring mark on the LPGA Tour. The Swede owns that record, which she achieved courtesy of a second-round 59 at the 2001 Standard Register PING.
Pak was on fire early with five birdies over her first six holes but she cooled down until a birdie at the par-3 16th.
The South Korean added a birdie at the 17th to finish six shots back in a tie for second.
Sophie Gustafson, who won this year's Samsung World Championship, finished alone in seventh place at 10-under-par 134 after a round of 66.
Karrie Webb, Mi Hyun Kim, Dorothy Delasin and Christina Kim shared eighth place at 9-under-par 135. Miho Koga followed at 8-under-par 136.
Laura Davies, Gloria Park, Laura Diaz and Soo-Yun Kang finished knotted at 7-under-par 137.