My Sister Who Regressed Wants My Fiance

I became engaged in my sister’s place, following our father’s command—he always favored her over me. To escape, I fled for a week into the public domain. Upon my return, my sister was already there, greeting me with a chilling calm. She declared she had changed her mind and demanded I step aside, now desiring the role of the Ghost Duke’s wife herself. Yet, amidst this, a mysterious peacock shows interest only in me. The confusion deepens when I discover her diary, revealing she has regressed from the future. Now, with knowledge of what’s to come, my returned sister is determined to claim my fiancé for herself.