Manga Personality.
An analysis on the personality of Sailor Mars, and how she acts around others. This is the manga version only, for the anime version go here.
Rei's personality is calm and measured. She is always elegant and ladylike, though occasionally prone to making snide comments. She is clearly a very caring individual but very withdrawn, and occasionally unsure of her self. Such as in her introduction in Act III where she doesn't help the parents of the children who have gone missing in her shrine. She generally acts on powerful intuitions, when she has an intuition it frequently helps her trust herself more.
Probably one of the most isolated of the senshi, especially the inner ones, (or, if you aren't a fan of the 'inner-outer' terminology the first senshi found by Sailor Moon). Rei attends a different school, and therefore occasionally misses out on some of the antics that the other inner soldiers get into. She doesn't seem to mind the isolation though. In fact, in a side chapter where Minako attends her school for a day one could say Rei enjoys her time away from the other senshi. Though she clearly also loves her friends.
Certainly the most mature around men, when the other senshi are falling over themselves to meet pretty boys, Sailor Mars is comfortable at an arm's length. Despite this distance she holds from men she is still very feminine. Another side story shows some hurt surrounding a man she may have loved and therein some reasoning behind this isolation. Rei is not the sort of girl who will let herself get hurt twice. She is a textbook ice princess, all the boys want her and she'll never give them the time of day.
Like all the soldiers, Rei is extremely loyal to her cause and considered one of the most powerful of the senshi (and I know we all say this of our favourites, but I think Rei does rank up there). She is the only senshi who has special powers when she isn't transformed. Always calm and collected Rei is a peaceful soul when happy and a fireball when angered.
Which is why, despite her serenity Rei can be prone to acting before she thinks things through completely. Such as her first appearance in Act III where she attacks Usagi, thinking her to be an evil spirit.
All in all, I vastly prefer the calmer, more level Rei Hino of the manga to the fireball in the anime. There is something so beautiful and enviable about the power she has and the way she is not afraid to use it in the defense of herself and her companions. She is courageous, sleek, and well an all around solid character—fighting crime in high heels.