Tomoe's sister has been tragically murdered. Her sister, Shikihime, a princess of the Kurayama Dynasty, met her untimely death in her chamber on the eve of her politically significant wedding. In the wake of this tragedy, Tomoe, her older sister, is approached by their father with a daunting request: to assume Shikihime's identity and proceed with the marriage as planned. Committed to her father's wish, Tomoe accepts this lifelong mission to lead a life of happiness in her sister's stead. Now as Shikihime, Tomoe arrives in the Duchy of Frostgard, a territory within the Iskaldt Rike Realm, only to be met with an unusual request from the Realm's fleet upon her arrival. This marks the beginning of Tomoe's journey alongside her husband to be, Shikuro, the Archduke of Frostgard.