Watashi wo Futta Hito no Kozukuri Aite ni Meizeraremashita

Tiana, a marquise's daughter, and Crown Prince Lagiras, who loved each other and vowed to remain pure until marriage, suddenly break off their engagement one day when Lagiras announces he will marry Tiana's cousin, Serage!? Three years have passed since her beloved fiancé and her close cousin married and became king and queen after the betrayal. Tiana, who lives quietly in her rural territory, receives a summons from the royal court! Filled with anger at the thought of being betrayed and now being summoned, she goes to the royal castle only to be told by the prime minister to become Lagiras's "childbearing partner"!? She thought she had no desire to be with her ex-fiancé, with whom her relationship was over—.

(Source: Shusuisha, translated)