Subaru

Subaru is an experienced Blade from the past who served as Haruka's mentor. She is a serious individual with strict discipline and great devotion to the Crescent Moons and their ideals, as well as her master, the Dragonian of her original era, though she was still a caring mentor for Haruka. Despite experiencing many traumatic events following her defeat against Ittou Hagane, she managed to stay utterly resolute in her mission. However, it did make her colder and harsher, particularly when faced with what she considered to be complaisance from her modern associates.

(Source: Wikia)