Naomi Osaka said her first Pan Pacific Open title win in her hometown was "special" after she beat Anastasia Pavlyuchenkova in straight sets.
Osaka, 21, who had twice finished runner-up at the tournament, beat the Russian 6-2 6-3.
The world number four said: "This is the city where I was born and that gave me a lot of power to play match after match.
"I love playing here and see you all next year."
It was Osaka's first title since lifting the Australian Open in Melbourne in January.
There was also tournament success on Sunday for Karolina Muchova of the Czech Republic as she thrashed Poland's Magda Linette 6-1 6-1 to win the Korea Open in Seoul, her first WTA title.
On the ATP Tour, Daniil Medvedev was victorious on home soil, defeating Croatia's Borna Coric 6-3 6-1 to lift the St Petersburg Open in Russia. It was a third title of 2019 for the world number four and an impressive response in his first event since his epic five-set defeat by Rafael Nadal in the US Open final.
At the Moselle Open in Metz, home favourite Jo-Wilfried Tsonga won the title for a fourth time, coming out on top 6-7 7-6 6-3 over Aljaz Bedene of Slovenia. Of Tsonga's 18 tour titles, 10 have come in his native France.