ITS THE OTHER SIDE OF A REINCARNATION STORY
the story of the soul of the original villainess gets ig trapped in her body while a reincarnated soul took over. The original soul Remillia and the reincarnated one Emi. Rem fell in love with the first person that ever showed her what love feels like, ultimately she seeks revenge for Emi when Emi faces a tough time with her rival, the "main character" who steals her friends and fiance through mysterious magic. Emi gets presumably trapped in her subconscious while Remilia (the original owner of the body) awakens and surfaces, exacting revenge against the bitch who practically ruined her beloved, Emis' life.
The One Within the Villainess