I made an account just to try and find this one book. This is Yuri btw. There’s a girl (think this is in a school?) and she goes to a new school and she hears rumors about Room 13 and how it leads girls in there and stuff. She is then attracted to the room and she finds a black haired girl (supposedly a ghost though didn’t look like it) and they talk (don’t remember if they had sex or not) then at the end of the book she is on a bench and on her phone(?) then it ends. It was posted this year on this site. Been looking for months