Mina stands at average height with a slim, athletic build. While the artists are cowards who refuse to give her muscle mass, the characters comment on it and Kikoru even asks Mina to give her workout tips. She has long black hair, brown eyes, and most notably... two beauty marks. One beneath each eye - high up on her cheek bones.
In the series we only get to see Mina in her officer uniform or her powersuit. The only time we get an inkling on her fashion sense is splash pages (like the graphic above). She seems to prefer simple business casual outfits.
While Mina may come off as cold and detached, she's actually quite emotional. The stiff and polite demeanor is a front to protect herself from looking weak or vulnerable - as those traits are unacceptable in her line of work. Yet her biggest motivators in life are the strong feelings she has in regard to other people (and animals). Mina is incredibly sentimental, and easily falls for things that bring a sense of nostalgia.
Mina is voiced by Asami Seto! Here is a compilation video with examples. It contains out of context spoilers.
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SUIT REFERENCE (nape of neck)