As long as they're feared, they'll exist. If humanity were to somehow forget the concept of the devil, it wouldn't exist, or it would simply not reincarnate.

[ Aki is, unfortunately, just used to breathing in bad shit. Smoker with minimal life expectancy. Pushing behind the cupboard, he sees nothing important and starts to continue his walk, shoes too loud in the quiet of the dusty room. ]

That's why we hunt them. It pays well, and it saves lives.