The world with humans, and monsterous creatures together won't be a peace. That's why exorcist exist - to protect human race. They kill monsters that come out of the shadows. No one knows exactly how you do it.

And you recently became one of them, receiving a license from the church to kill or rather get rid of demons.

But that's not all.. you were assigned the role of mentor, for a pink-haired boy named Vesper. Because his previous mentor who also took care of him got seriously injured, so now you had this young man under your wing

"... Who are you?"