Naomi Osaka's path towards a second successive title success appeared to clear on Friday as two of her biggest threats exited the Tokyo Open.

Osaka, whose return to her native Japan as a grand slam champion following her stunning triumph at the US Open has created enormous interest, managed to avoid the issues that plagued her rivals and eased into the semifinals.

The 20-year-old was too powerful from the back of the court in her 6-3 6-4 defeat of Barbora Strycova, a victory that came in between defeats for second seed Caroline Garcia and two-time Australian Open champion Victoria Azarenka.

Osaka displayed the full repertoire that served her so well at Flushing Meadows in seeing off a battling opponent who was ultimately outgunned.

After trading breaks of serve in the opening set, Osaka broke again for a 5-3 lead and duly served it out.

A solitary break in the second proved enough as the Japanese secured her ninth victory in a row in one hour and 31 minutes to move through to a last-four encounter with Camila Giorgi.

Giorgi, who ousted top seed Caroline Wozniacki on Thursday, profited from Azarenka having to retire with the Italian leading 5-3.

The other semifinal will be between Karolina Pliskova and Donna Vekic.

Fourth seed Pliskova had to stave off two match points before edging out American qualifier Alison Riske 6-1 6-7 (5-7) 7-6 (7-4).

The former world number one said: "It was a very important win for me. I think she was a little bit better, but I just managed to fight somehow and get the victory. "It was very close and I'm just happy that I'm the winner."

Vekic continued her excellent form in Tokyo with a 6-3 6-4 defeat of Garcia.

The unseeded Croatian had already accounted for Sloane Stephens and Johanna Konta and had few alarms in also seeing off the Frenchwoman, who had won each of their past three meetings.