Heartless, MADK Recommendations
Both of these are yaoi about a relationship between a flirtuous (but powerful) demon and a human they are (to an extent) protective of. As both mix sex and gore, they are not for squeamish readers.
Both are gory BL manga about a relationship between a Demon and a Human. While Heartless takes place in the real (human) world, MADK takes place in hell. Both demon main characters are manipulative, but try to protect their human partner somehow.
