The Japanese star shot a six-under par round of 65 at the fifth major of the LPGA season to take a one shot lead over Suzann Pettersen of Norway, Se Ri Pak of South Korea and Sandra Gal of Germany.
Christina Kim comes next on four-under while Lydia Ko, Karrie Webb, Michelle Wie and Lindsey Wright all shot 68s for three-under.
Inbee Park, who has won three of the four Majors this year got off to a poor start though as she shot a three-over par round of 74.
The players finally took the course after Thursday's play was a wash-out due to bad weather.
- Sports & Recreation
- Suzann Pettersen
- Karrie Webb
- Michelle Wie
- Se Ri Pak