Japan’s world number four Naomi Osaka says she is “most comfortable” playing on hard courts.

Osaka is enjoying a strong run of form at the Pan Pacific Open in her home city Osaka, beating Yulia Putintseva 6-4 6-4 to reach the semi-finals.

Two-time Grand Slam winner Osaka, 21, had not won a set in three previous encounters with Kazakhstan’s Putintseva, 24.

“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.”