Japan's world number four Naomi Osaka says she is "most comfortable" playing on hard courts.

Osaka, 21, is enjoying a strong run of form at the Pan Pacific Open in her home city Osaka, reaching the final by beating Belgium's Elise Mertens, 23.

The two-time Grand Slam winner cruised past Mertens 6-4 6-1 in her second game of the day, after overcoming Kazakhstan's Yulia Putintseva 6-4 6-4.

"For me, I learned a lot from when I played her at Wimbledon," Osaka said.

"And I know that a hard court is where I feel most comfortable."

Osaka added: "Also, I'm playing in Japan, so I thought I had the advantage this time around."

The reigning Australian Open champion will play Russia's Anastasia Pavlyuchenkova in the final, after the 28-year-old beat Germany's Angelique Kerber 6-3 6-3 in the other semi-final.