bl/gl novels with the protagonist and love interest growing romantic feelings for each other despite one, the other, or both being:
1) a non-human (e.g. a god, a dragon, a ghost, a demon, etc.)
2) a human that takes on a non-human form/that becomes a non-human (e.g. an animal, a system, a mermaid, a zombie, etc.)
3) a non-human that becomes a different type of non-human (e.g. an elf becomes a plant)
4) a non-human that becomes a human/that takes on a human form
5) a half-human or a demi-human
note: for no. 2, the protagonist or love interest may or may not return to being a human.