Claymore 2 - Norihiro Yagi

A Claymore - a female warrior named for the sword she carries - travels from medieval village to village to destroy Yoma, monsters who disguise themselves as humans and who are almost impossible to kill. Claymores are half-humans, half-demons who willingly transformed themselves by mixing their blood with monster's blood. Claire, nicknamed silver-eyed killer, is such a powerful Claymore, she can slay a Yoma using only one hand. But she must constantly struggle to keep from becoming a monster herself. Claire and the orphan Raki travel to the town of Rabona, where a Yoma has been stalking the priests inside the cathedral. The creature could be one of the guards, or even a priest, but this time Claire won't be able to sense its aura. Does she stand a chance against the stealthy Yoma?