Unknown entities known as "Witches" roam the cities. They exist solely to destroy humans and turn them into one of the Witches. There is a sector in the government known as the Suppression Corps that specializes in dealing with these Witches, who are completely immune to conventional weaponry. Hensel Takamine is the leader of this group, and has an extreme hatred towards the Witches. With his sword imbued with the powers to eradicate Witches, he fights to avenge his sister who was murdered by these monsters.

(Source: MangaHelpers)