@rozoyahee protagonist liked to cross-dress and wished to become a woman. Under certain date and time, a demon and a female doppelgänger came out of mirror and made deal with him. In return for letting him having this female body (in protagonist's ideal image), she will get her soul when he dropped dead. Protagonist agreed then had sex to complete to deal. The demon then killed his male body.
He woke up next day in the female body exactly like the one he saw yesterday and it wasn't a dream (soul transfer). Maid came to room, noticed that the protagonist (male body) is dead. They believed the woman (who's now has the soul of protagonist) killed to protagonist and subsequently (imply) that the household killed that woman.