When her mom goes missing, three-year-old Lotilucia stumbles on a magic crest that transports her to the estate of House Frodium, one of the empire's most powerful noble families. Little Lottie immediately recognizes Duke Damian Frodium as her dad; he is the so-called "Monster Duke" of demon descent. Once taken into the house, Lottie does her best to stay out of his way. But then she stumbles on a magic book that shows her a story about Duke Frodium's adopted daughter replacing his dead daughter named Lotilucia! Lottie is shocked but also emboldened by the prophetic tale. If she is meant to die anyway, she might as well be her cheeky self and do as she pleases! This new Lottie wins over her demon dad along with his staff, but will she manage to stay alive and thrive as the Monster Duke's daughter?