can't remember the name of a book

I believe it's classified as yaoi, and I just saw it at the book store but I don't remember the title. All I remember is that there is a guy who is cursed and her turns into a demon (at night?) and he has a friend who tries to help him lift the curse. Also when he turns into a demon, the only way he can be tamed is through sex.

I believe that the title was very similar to another non-yaoi title (if that helps, lol).

I found it (by pure chance). It's Crimson Spell (I was thinking Crimson Hero). Anyone read it before?

i have

but i was confused because i read another like it a other yaoi genderbender story called "im cursed to turn into a girl everynight and have sex with all the knights" or something like that i dont remember