Earth has been taken over by demons and devils and other hellions of the underworld. The world is now chaotic and unruly; it's every man for himself. There's only evil in this world. Not even one devil has even a meager amount of good in them.
However, there is one rule that every demon lives by. Having taken the old human term "Stranger Danger," they modified the phrase to say, "Angel Danger." Children are told horror stories of flaming swords and holy words and mighty power that will swiftly bring any devil it its knees. Seeing an angel is incredibly rare. They typically stay up in heaven and don't bother with Earth's demonic inhabitants. It's drilled into every child's head that if you ever see an angel, the only thing you can do is run and pray to Lucifer's father that you don't die.
C1 is a demon, the worst of the bunch. C1 instills fear into everyone they see, intimidating everyone into pieces. But what do they do when they C2, an angel roaming the earth? And how do they react when they discover C2 isn't going to obliterate them? How do they respond to the fact that C2 is actually kind and compassionate, attributes they've never before seen in their life?
(Also just a side note I do prefer straight romances)