A lonely demon picks up a dying girl... In the countryside of 19th century France, Nini, a girl abandoned by her parents and on the verge of death, meets the beautiful demon named Dantalion. She makes a contract with Dantalion and chooses to live as his familiar in the demon world, but what awaits her is not a harsh life but the generous protection of a thoughtful master who loves sweets. The warm and cozy life with Dantalion, a veterinarian specializing in magical beasts, eventually melts the frozen parts of Nini's heart.