Sara

Sara is Kagetsu's sister and a Tiara's childhood friend. A sweet, gentle girl with a weak constitution, she has untapped ability as a Neutralizer. She mysteriously disappeared before the Throne of Yord incedent began. It is implied at the conclusion of the "Throne of Yord Saga" (and is indeed the thing that saves Tiara's life) that Sara is and always has been a part of the Throne of Yord, and that she was destined to joined to it from birth.

(Source: Wikipedia)