Nao is an upbeat, quirky, loyal and motivated girl. Easily frightened, Nao can become frantic over stress-inducing situations. Her sometimes overwhelming panic can be quelled by her own force, but only if a person she cares about is in more danger than herself. She has a deep attachment to her mentor Mishima and often relies on him to get her through difficult times. 

I imagine Nao's voice to range from medium-high to high. The actor must be able to show a wide variety of emotion.