Another world (the protagonist thinks they're in a book or made up world, but aren't.)

These stories features protagonists who either think that they're in a fictional world (book, game, etc.), they've possessed someone else's body, and that "they're not the real [insert name]", for example 'Father, I Don't Want This Marriage', 'My Stepdaughter is a Bunny', 'Obsessed With Shuelina', or 'Shall We Bathe, Your Grace?'.