Helped by a burst of three birdies in a row on the back nine at Seta Golf Club in Shiga, the Scottish No 1, who was playing in Japan for only the second time and first as a professional, finished with a 20-under-par total.
Dropping just two shots during the week, she won by an impressive four strokes from home player Kana Nagai after she also closed with a 65, with Swede Linn Grant, who bogeyed the last for a 67, one further back.
It had only been the second time that Dryburgh, who was born in Aberdeen but has lived in Beaconsfield in Buckinghamshire for most of her life and is now based in New Orleans, had found herself in the final group on the LPGA Tour.
But, using her experience from ending up in tie for eighth in the 2021 Cambia Portland Classic, she comfortably got the job done and did so in a field that included new world No 1 Atthaya Thitikul from Thailand.
One behind Japan’s Momoko Ueda at the start of the day, the 29-year-old opened with three straight pars before picking up birdies at the fourth and seventh to move to 15-under. That put her one in front of both Ueda and Grant after the Swede, who has a Scottish grandfather, stormed to the turn in 31, four-under.
Dryburgh then birdied the par-4 11th before quickly bursting clear at the top of the leaderboard as she made three gains in a row from the 13th, meaning she headed into the final three holes with a three-shot cushion.
She holed a testing par putt at the 17th to keep that intact as she headed to the last and a birdie-4 to finish was the icing on the cake.
Dryburgh joins Catriona Matthew, Janice Moodie and Kathryn Imrie as Scottish winners on the LPGA Tour, with this being the first tartan triumph on the circuit since Matthew landed the 2011 Lorena Ochoa Invitational.
“I can’t (believe it), to be honest,” said Dryburgh of a success worth $300,000. “I was in Korea last week with friends and said to them ‘I will mention you in my speech’ but just as a joke.
“It is overwhelming, to be honest. It’s been a dream of mine for a long time and a lot of hard work has gone into this and it means so much as it is a life-changing win.
“I was surprisingly calm. When I’d dreamt of this moment, I thought I would be super, super nervous. I was nervous, I’m not going to lie, but I was incredibly calm, to be honest.
“The fans were amazing fans. We get clapped on to every tee and the vibes are just so good and we just lapped it up.”
Becoming emotional, she added: “My parents mean so much to me and they’ve done so much for me in golf. I’d also like to thank my caddie Paul Heselden] and my coaches back home. I’ve done amazing work with them all over the years and it means a lot.”