Lady Demirka is the beautiful, intelligent daughter of the powerful Grandshed duke family who has received a special education from an early age to become a candidate for the crown princess. She has always assumed she would marry into the royal family, but when the timid prince rejects her, Demirka reacts in a most unusual way. Rather than falling into despair or anger, the young lady with an unparalleled strong mentality remains completely composed and calmly begins taking action to ensure the engagement is broken off.

The story follows Demirka as she navigates this reversal of fortune, focusing on her strategic and unflappable approach to what would normally be a devastating social blow for a young noblewoman. The series, originally written by Amano Angela and adapted into manga by Hatoi Fumi, is set in a noble aristocratic world where engagements and royal connections determine social standing. As the narrative progresses, Demirka overcomes various adversities while the mystery behind the prince’s decision to reject her deepens, drawing attention to the mastermind who may be orchestrating events from behind the scenes. The plot explores how an exceptionally mentally strong villainess uses her intelligence and training to take control of her own destiny rather than accepting the role typically assigned to a rejected fiancée.