Five years ago, Suzune’s peaceful life as the daughter of a declining aristocratic family was shattered when a gentle neighborhood priest caught sight of her blood and flew into a frenzy, leaving a deep, permanent scar across her back. Branded a cursed child who leads kind-hearted people astray, she was sold by her debt-ridden family to a pleasure district island called Yūkaku Island—taking the place of her twin sister, Makie. Forced to wear a mask to suppress her supposed curse, Suzune endures daily abuse and backbreaking labor as a maid, treated as less than human.

Her fate changes when Yakumo, the head of a powerful conglomerate that controls the waters around the island, pays a visit. Ominous rumors surround him: any courtesan chosen to spend the night with Yakumo remembers nothing afterward. But it is Suzune’s unique, alluring scent that draws him. When a fire devastates the island and Suzune is framed for arson by her jealous sister, Yakumo intervenes and takes Suzune away.

Suzune soon discovers Yakumo’s secret: he is a vampire, and her blood is no ordinary blood. It is Ōkakechi, an exceptionally rare and exquisite vintage that vampires prize above all else. Yakumo declares that in exchange for her blood, he will take her as his wife, but he makes it clear that their marriage is purely a practical arrangement—she is his food source, not a beloved partner. Yet life in Yakumo’s isolated island mansion, though initially cold, slowly begins to offer Suzune something she has never known: safety, warmth, and small acts of kindness.

As Suzune tentatively adjusts to her new role, her family—greedy parents and a scheming sister who harbors deep resentment—reappear, demanding money and plotting to tear the couple apart. Meanwhile, the true nature of Suzune’s blood, the history of vampires and humans, and a growing, unexpected tenderness between Suzune and Yakumo begin to emerge. What starts as a transaction between a discarded girl and a cold-hearted vampire gradually becomes a story of trust, self-worth, and a love that defies the boundaries between predator and prey.