I think the point of this story is that people can be extremely self-centered and egotistical but still be good people or just people living their lives, even Kou is extremely self-centered in a way he does help people a lot many are better after meeting him than before so his type of self-centeredness isnt bad.
Hatsuka clearly has a screwed up notion of relationship but he doesn't seem to devalue his "servants" lives, he does see them more as possessions though.
There is the other ones, Midori seems to only be living her life how she wants, Seri has found a partner that she feels comfortable with and that she values (even if she is still "playful"), i dont know how Nico or the other one deal with their relationships.
I am worried that they would kill Kou, but the death threat always seemed more like something they say to incentivize secrecy than their true disposition to kill a person, like Kou said they are creatures of instinct.
But there is the last vampire girl that we suspect to be the one Kou's friend was infatuated and she does seem to have a bad personality, sure this isnt confirmed yet.