Shirou Fujimoto

Shirou Fujimoto was Rin and Yukio's guardian and was also considered to be one of the most powerful Exorcists in the world. He was thought to be the only man in the world that was able to sustain possession by Satan himself and thus Satan was constantly after his body. Fujimoto had a familiar sith cat demon, which he called Kuro, that Rin had inherited. He was a confirmed Aria, Dragoon and tamer and could possibly have been a Knight and a Docter as two of those who have studied under him have become these. He was said to be the strongest exorcist on the planet and was the only one to gain the rank of Paladin, the highest rank of the exorcists.