The genre is fantasy. Sort of medieval London setting. Protagonist is a special corps military/police officer with a huge sword. The special corps kills witches that infect humans with virus turning them crazy/into zombies. Only the special corps can kill the witches with the weapons made out of special metal/infused with something. For some reason (?) Protagonist hates witches with a vengeance. In chapter 1, he stumbled into a girl when he was chasing after a witch with his troops. Then the girl used a magic that destroys the witch. Turns out the girl is also a witch. In chapter 2, protagonist woke up after recovering from his injury. The girl had embedded some curse in his body which increase his affinity to sense witches. Confided in a doctor who told him to bring the witch girl or else he will completely succumb to becoming a witch. Next he was chasing down another witch with his troops again and came across the witch girl in this mission again.
Thanks for any help.
