The One Within the Villainess is a Manga/Manhwa/Manhua in (English/Raw) language, REINCARNATION series, english chapters have been translated and you can read them here. You are reading The One Within the Villainess chapters on ManhwaZ, fastest updating comic site. The Summary is
In order to clear the name of 'Emi,' a girl who had reincarnated as Remilia, the villainess of an otome game, the real Remilia who had been watching all along inside awakens. Now it's time for the true villainess' revenge to begin!