セイバー

Saber is Shirou's Servant. Loyal, independent, and reserved, Saber acts coldly but is actually suppressing her emotions to focus on her goals.

Her class is considered the "Most Outstanding", with excellent ratings in all categories. Since her Master cannot effectively provide her with Mana, she minimizes her activity to preserve her energy. Saber is frustrated by Shirou's "protective" tendencies, believing his erratic and reckless behavior will jeopardize her chances of winning the Holy Grail War./

From url=http://en.wikipedia.org/wiki/List_of_Fate/stay_night_characters