Russia's Veronika Kudermetova won the Pan Pacific Open in Tokyo on Sunday, upsetting tennis' world No 4 Jessica Pegula in straight sets.
The 19th-ranked Kudermetova overwhelmed the American 7-5, 6-1 in an hour and 24 minutes.
"I knew it would be a tough final... I need to fight for every ball and today it worked really well," she said.
"I'm really happy that I managed to win my second title," said the 26-year-old, who won her first WTA singles title in Charleston in 2021.
She beat Pegula in three sets on the clay in Madrid this year.
"I played better today than in Madrid," Kudermetova said, adding that Pegula "always fights and plays solidly every match".
"Today I followed my game and my plan" to play agressively, she said.
Kudermetova had a tough semifinal, needing three hours and 25 minutes to defeat Anastasia Pavlyuchenkova.
She stunned four-time Grand Slam champion Iga Swiatek in the quarters.
Pegula was aiming for her second title of the season following victory last month in Montreal.
Kudermetova "put a lot of pressure on me at the beginning so it made it very tough", the American said.
"Luckily I was able to get back to the first set but I just don't think I was serving well enough... She was a better player today."
The 29-year-old went into the US Open dreaming of a first ever Grand Slam title, but her campaign came to an abrupt halt as compatriot and close friend Madison Keys recorded a dominant win in just 61 minutes.