Every hundred years, the Monster's Bride is chosen as a sacrifice to a demonic creature confined somewhere within the country. When Stella's younger sister Lilinette is selected, Stella, the adopted eldest daughter of Viscount Quinwitch, volunteers to go in her place. She is sent to a castle to become the bride of a cursed, blood-soaked vampire named Lavi (also written as Ravi or Rabi).

Stella discovers that behind the blood and fangs, the monster harbors a deep loneliness. Lavi is a vampire who has given up on everything, bound by a curse that isolates him. The narrative follows their developing relationship as Stella's affection and determination challenge his despair. In a pivotal moment, Lavi sucks Stella's blood, which is tainted with magical powers, creating a deeper bond between them as he struggles to save her. The story is a romantic drama exploring whether their love can survive the curse that surrounds them.

The manga is set in a historical fantasy world centered around the cursed castle where Lavi is confined. Notable narrative arcs include Stella's initial sacrifice and journey to the castle, her first encounters with the vampire and her growing understanding of his pain, the revelation of her blood's magical properties, and the escalating challenges as external forces and the nature of the curse threaten to tear them apart.