Mavis von Austien

The official leader of the Crimson Vow (although it is always Reina that does the actual "leading"), a swordswoman of noble birth. After running away from home in the hopes of becoming a knight, she met the other members of the Crimson Vow at the Hunters' Prep School and helped to form the party. She is tall and has an androgynous appearance, making her popular with other girls.

(Source: Wikipedia)