Reference for the voice can be heard here!

While she has a "to the max" side as a magician, Himiko also has a very lazy side and finds putting in the maximum effort to be too much trouble. She constantly calls things tiresome and appears disinterested in things other than magic, refusing to do several things because it's "such a pain". She also struggles to communicate her feelings to others, claiming that talking wears her out and generally appears to be spaced out. She also has a bit of a droning, monotone voice, making her one of the most "tired" sounding female characters of the entire series. While she is occasionally anxious to the point of severe trembling and stuttering, there are also moments when she just appears mildly annoyed during horrible situations and doesn't seem to fully realize what is happening. She is also notably childish, taking pride in things like brushing her teeth or going to the bathroom by herself, and constantly talks about her magic or other completely irrelevant topics during inappropriate moments.