Formerly, the Fallen Daughter of the Duke, Volume 3

Betrothed to Prince Asbert of the great kingdom of Noston, Claire is shocked when the engagement is suddenly annulled. More than that, the new consort to the throne is none other than her sister, Charlotte! As the daughter of the now disgraced duke and scorned as a villainess, Claire leaves everything she knows and sets out on a journey to find her true self.

But wait, isn't that's the plot of the game "Upstart ♡ ETERNAL LOVE" on its hardest difficult setting...?