Overnight leader Lee Bo-mee equaled a course-record 65 to secure her second title of the season at the Hisako Higuchi Ladies on Sunday.
The South Korean sank four birdies in a five-hole stretch on the front nine at Morinaga Takataki Country Club and picked up three more strokes after the turn to finish five strokes ahead of compatriot Ahn Sun-ju.
Lee, who won the Japan LPGA Championship in September, finished with a tournament record of 15-under 201. Her fifth JLPGA title win earned her ¥12.6 million in prize money.
"My aim for the final round was to go under par and I was focused and tried hard. I am happy to win the title," said Lee. "I'll keep on giving my best."
Ahn finished alone in second after a 69, and China's Feng Shanshan also closed with a 69 and followed in third at 9 under.
Yuko Fukuda set the course record of 65 earlier in the day to move up to a tie for fourth after starting the day tied for 28th. She finished at 8 under with Ayaka Watanabe and South Korea's Shin Jiyai.