Are these succubi demons from Hell (or, at least, descended from demons from Hell) or, on this version on Earth, are succubi essentially just mutated humans like in Demi-chan wa Kataritai/Interviews with Monster Girls?
Not that there's anything wrong with being from Hell, Vignette in Gabriel Dropout is a demon but she's the most angelic character in the manga and Gabriel Dropout Hell is just like Earth except a little mistier.