I can't recall the name of this manga I read awhile back - Main character is a HS girl who dies (I think) and becomes a ghost meets up with another ghost girl (yandere) at her school who proceeds to kill the main character's crush and then the rest of her class so they can all be ghosts with her. I remember it having a fairly twisted sense of humor with a pretty liberal amount of smut content, and eventually some yuri between the two ghost girls?

I think Alignment You You is what your talking about and not so much smut as its a full on h manga.