British No. 1 Katie Boulter exited the Pan Pacific Open at the semifinal stage on Saturday after a 6-4, 6-4 defeat to Sofia Kenin.
Boulter had been looking to claim her third Tour title of the year but Kenin eased past her Boulter inside 90 minutes to reach her first WTA singles final since San Diego last year.
Kenin, 25, won the Austrlian Open in 2020, as well as finishing runner-up at the French Open, and reached a career-high No. 4 that season, before injuries, illness and off-court issues saw her drop down the rankings.
She will face Zheng Qinwen in the final in Tokyo.
"I think she's a really good player and she has a good ground stroke and she has some great drop shots," Zheng, who beat Diana Shnaider later on Saturday, said of Kenin.
"Of course, if she's in the final, it means she's really tough to beat in this tournament. I'm just going to try my best tomorrow and let's see what happens."
Information from Reuters contributed to this report.