Claymore, Vol. 1 by Norihiro Yagi

[Viz] A New York Times best selling, multi-arc, character-driven story with great battles and strong-willed females that will appeal to males and females alike. In a world where monsters called Yoma prey on humans and live among them in disguise, humanity's only hope is a new breed of warrior known as Claymores. Half human, half monster, these silver-eyed slayers possess supernatural strength but are condemned to fight their savage impulses or lose their humanity completely. A village is gripped by fear and paranoia when a Yoma claims six lives. The Claymore who is sent to slay the creature isn't what the villagers expect at all. In fact, she seems more monster than human.