Mysteriesss

MC is a broke writer whose suspicious neighbor may be related to the serial killings nearby...

Everyone in this story is fucked up.
Not exactly a mystery, but every chapter feels like something new and major has been revealed about the characters

The MC believes she transmigrated into a romance fantasy novel, where she is a sickly daughter of a rich family. Her family, servants, and fiance act very suspiciously, but its all in the name of romance cliches, right?