TOKYO, 9 Nov 2014 (AFP) - The 21-year-old beat compatriot Lee Il-Hee and Japan's Kotona Kozuma after all three women finished tied at 11-under 205 in Japan on the final stop of the tour's Asian swing.
The victorious Lee and Kozuma both carded final rounds of 69 while Lee Il-Hee returned a 70 to set up a marathon three-way playoff.
"It was my first playoff ever, so before it began I was very nervous," the champion told reporters after tapping in to bring the drama to a close. "I just kept playing and made the pars and birdies. It was really exciting when the last putt fell."
Lee, who made her LPGA debut in 2012, pocketed a top prize of $180,000 after becoming the seventh South Korean to win on the tour this season and following world number one Inbee Park's victory in Taiwan last weekend.
Britain's Laura Davies, who held a share of the lead after the second round and was bidding to become the oldest winner in LPGA history at 51, fired a 71 to finish one stroke behind the leading trio.
Australian Karrie Webb and Morgan Pressel of the United States were also among the group of nine players tied for fourth place.
Defending champion Teresa Lu of Taiwan carded a 67 to finish tied for 13th, while American world number two Stacy Lewis, who won the title here two years ago, was six strokes adrift after a closing 69.