@icarushector if i remember the first couple of chapters right, it was stated that demonkin is actually pretty evil, succubus however tended to not have any violent thoughts towords humans (why would they, they need them to live, its a mutual benefit) however humans hate succubus the most because they rob humans of their sanity and they naturally fall victim to lust.... which makes sense i suppose, so while there are actually some demonkin (such as the lizardman and the cat(?) girl which are actually demonkin) that can coexist with humans, succubus cannot, even if they theoretically could on the surface
as for the demonlord... hes an incubus obviously, his aunt is a succubus, and he has perversions, its obvious hes an incubus, this means that the 3 demonkin the knight order are after are all succubus/incubus which have been deemed as inherently hostile to human society, even if not hostile to humans directly.