Mifuyu Mizukagami

An eighteen year old third year student of Clamp Campus' high school division, Class Z. Despite her innocent appearance and air-headed personality, she is a master swordfighter. She carries around her master blade, Kotetsu, all the time and will cut down any enemy who dares to cross her path. Mifuyu is based on the player character that was used by Satsuki Igarashi. Source: Wikipedia