Vergil Grayson, a third year in Kuoh, had the misfortune to become a target of Fallen Angels and their victims. Fortunately, Rias Gremory has decided to take him as her Servant, but, instead of becoming a Devil, he became it s complete opposite, a unique free Angel. Thrust into a world of Devils, Angels and other beings, Vergil stands vigil, with the gift of God in hands of his.