Gemma Dryburgh on Sunday became the first Scot to win on the LPGA Tour since 2011, as new world number one Atthaya Thitikul of Thailand tied for 10th on 10-under.
Atthaya was playing her first tournament since becoming the second-youngest world number one in women's golf history this week, following a stunning debut year on the LPGA Tour.
The 19-year-old, who has won twice on the tour this season, said she was not happy with the result but was "still in a good zone".
"I think what I've achieved now -- I know when you look at it, it seems like a lot but I don't think that much because this is just my first year on the tour," said Atthaya.
"There's a lot of work to do. I think I am still working and getting better, improving."
Dryburgh stayed "surprisingly calm" to claim victory by four strokes at the LPGA Japan Classic.
The world number 199 rattled off seven birdies with no bogeys on her final round to capture her first title on the elite LPGA Tour.
She also gave Scotland its first winner on the tour since Catriona Matthew at the 2011 Lorena Ochoa Invitational.
Dryburgh began the day one shot behind leader Momoka Ueda but carded a final-day score of 65 to put her 20-under overall, four shots clear of Japanese runner-up Kana Nagai.
The 29-year-old from Aberdeen said winning the tournament was "overwhelming" but showed no signs of nerves as the prize got closer.
"I was surprisingly calm," said Dryburgh, who finished her round with a birdie.
"When I dreamt of this moment, I thought I'd be super, super nervous, I'm not going to lie. But I was incredibly calm, to be honest."
Dryburgh became the fourth different Scot to win on the LPGA Tour.
She made a steady start with two birdies on the front nine but really caught fire as she homed in on the finish.
Dryburgh said a three on the par-four 11th was "the turning point" as she fired off five birdies in the space of eight holes.
"I had a really good shot there yesterday and hit the same club today, so I was confident I could do it again," she said of her birdie on the 11th.
"But yeah, had an incredible shot there and it was a nice birdie on that one."
Sweden's Linn Grant finished third, one shot behind Nagai.
Ueda, who had led from the first round, fell away to a tie of fifth after a disastrous final-round 74 that included three bogeys and a double-bogey.
The LPGA was returning to Japan for the first time since 2019 for the event, which was co-sanctioned with Japan's JLPGA.
The tournament was contested as a JLPGA-only event in 2020 and 2021 because of the coronavirus pandemic.
Fans came out in force at Seta Golf Course in western Shiga Prefecture and Dryburgh said she was "lapping up" the atmosphere.
"They are amazing fans," she said.
"We get clapped onto every tee, which is amazing. The vibes are just so good."
