The third-year pro leads the Japanese professional women's tour with eight victories this season.
Runner-up Mone Inami wins a playoff with Lydia Ko to capture Japan's first medal in Olympic golf.
Defending champion Inbee Park is three strokes back, while Japan's Nasa Hataoka is tied for 16th.
Team Japan had 338 athletes at the 2016 Rio de Janeiro Olympics, and the last time Tokyo hosted the Olympics in 1964 there were a total...
Inami has won four of the eight JLPGA Tour events since early March, including last weekend's Fujisankei Ladies Classic.