Once a year on a cold midwinter night in the Empire of Hartan, a fortress of frost appears, revealing the resting place of a blue-eyed demon said to grant any wish – for a price. When Princess Estelle of Hartan flees her abusive imperial family, she is encounters the otherworldly Frost Fort and makes a pact with Satael, the blue-eyed demon of legend. Pledging her body and soul to him, Estelle begins to plot for the crown.