The first sketch of Tann, this image is meant to be her simulation appearance.

These sketches are Tann's actual appearances. Based on the story, due to her terrible living habits, she is literally a walking skeleton with thick eye bags. Also, take note of her clothing, which is basically a labcoat A later version of Tann's virtual appearance. Notice how her eye bags are reduced and her face is slightly rounder as well as long hair. Tann is those kinds of people who use photoshopped images as their profile pictures. Her clothing changes to a more casual and teen-ager style with hoodie and jeans.