"Vanitas" is a manga series set in a fantastical 19th-century Paris, blending elements of steampunk, gothic aesthetics, and supernatural intrigue. The narrative centers on the conflict between vampires and humans, exploring themes of identity, morality, and the nature of curses. The story begins with Noé Archiviste, a young vampire traveling to Paris in search of the "Book of Vanitas," a legendary grimoire said to hold the power to either save or destroy vampires. Upon arriving, Noé encounters Vanitas, a human who claims to be a doctor specializing in vampires and wields the Book of Vanitas. Despite their contrasting personalities and ideologies, the two form an uneasy alliance to uncover the truth behind the book and its connection to a mysterious affliction known as the "Curse of the Blue Moon."

The Curse of the Blue Moon is a phenomenon that corrupts vampires, twisting their true names and driving them to madness or death. Vanitas, who bears the name of the infamous vampire Vanitas of the Blue Moon, seeks to use the book to cure afflicted vampires, believing it to be his purpose. Noé, driven by curiosity and a desire to understand the book's origins, accompanies Vanitas on his journey. Their investigations lead them to confront powerful figures within the vampire aristocracy, including the enigmatic Charlatan, a shadowy organization manipulating events from behind the scenes.

Key characters include Jeanne, a vampire knight bound by a curse and torn between duty and personal feelings, and Dominique de Sade, Noé's childhood friend with a complex relationship to both him and the vampire world. The series delves into the histories and motivations of these characters, revealing layers of betrayal, loyalty, and tragedy. As the story progresses, the line between hero and villain becomes increasingly blurred, with both Noé and Vanitas grappling with their own moral dilemmas and the consequences of their actions.

The narrative is structured around episodic arcs, each focusing on a specific case of the Curse of the Blue Moon while advancing the overarching plot. Themes of free will, the nature of evil, and the duality of salvation and destruction are woven throughout the story, creating a rich and layered exploration of its characters and world. The series balances action, mystery, and emotional depth, making it a compelling entry in the supernatural genre.