I keep on proposing this, alongside a comprehensive list/link with no real luck. It's rather simplistic, mostly as a means to grab someones attention ( clearly hasn't worked so far, ha! ), perhaps I need to rewrite it or something, when I have the time again.
Demon x Human ( Horror )
An ancestor was once a great demon slayer. He was a good man who married young but during his work, he was having an affair with a Demon ( spent to much time looking into the darkness and eventually it looked back into him ). However, she eventually betrayed him. Heartbroken and dying, he cursed her to remain apart of his family forever, serving the eldest of his future son and grandsons for eternity as punishment, even though he himself originally cheated on his wife to be with the Demon. This curse has continued and my character next in line. Since their spirits are bonded, for better or worse he'll be able to do more things than used to once he reached a certain age. He finds himself with a peculiar set of abilities/powers, but they're nothing when compared to the sheer abilities of the Demon now bound to him through his ancestors curse.
The world itself isn't devoid of 'evil', a subjective debate depending on where you stand upon the bell curve, but my character finds himself taking up his ancestors old mantel, becoming a Demon Slayer for profit, all while trying to maintain some semblance of a social life.