Hiyoku no Tori

The setting is ancient-China. Our main characters are poisonous (sometimes domesticated) harpy-like creatures, who get their poison and the ornate coloring that they’re so proud of, from the toxic plants which they eat.

This is a yaoi focusing on the (somewhat fraught) relationship between two such harpies.

If you’re here for a human x harpy relationship… Well, let’s just say you won’t be disappointed either.