Nara, a wild-card entrant who was born in Osaka, got by Polona Hercog 7-6 (7-4), 2-6, 6-1. She dropped her serve four times but three of those were in the second set. She put the match away by going 3-for-3 in break chances in the third set.
Nara will be seeking her first WTA finals berth Saturday when she meets fifth-seeded Eugenie Bouchard, who defeated Barbora Zahlavova Strycova 2-6, 6-4, 6-1 in the quarterfinals. Bouchard didn't manage a break opportunity in the first set but piled up 12 -- converting five times -- in the final two sets.
No. 3-seeded Samantha Stosur had 12 aces during her 6-1, 3-6, 6-3 victory over Misaki Doi. Stosur won more than two-thirds of the points on serve.
Madison Keys, the No. 6 seed, defeated Zheng Jie 6-3, 6-1 by taking more than half (25-of-47) of the points off Zheng's serve and finishing with five breaks.
Saturday's semifinal pairing will be the first career meeting before Bouchard and Nara. Stosur beat Keys 6-3, 6-4 earlier this year in their only previous match.