World's End Blue Bird
I've read this mangaka previous works, and they always have this details art style and most importantly very detailed lore, creating an interesting world just for a BL manga. The other manga is Beast of Blood, that one also has an interesting concept. This is what I'd call premium BL manga. Also, first look or multiples dozen looks at the cover art, I'd never would've guess its by this same manga that created Beast of Blood because this cover art is extremely different, I can't tell the art style based on the cover.
Kyuuketsuki to Yukai na Nakama-tachi