Befitting of her occupation as a professor, Rei acts mature and professionally most of the time, making her seem cold and look older than she really is. She absolutely dislikes having her time wasted, so she always gets to the point quickly and speaks in a blunt manner. She can also be condescending towards others, refusing to converse with people she does not find worth to talk to. Due to this, she can sometimes go as far as ignoring a person if she saw a lack of worth in them.