In the centuries following Armageddon, the appearance of a second moon, dubbed the "Vampire's Moon," ignites a conflict between humanity and the Methuselah, vampiric beings that subsist on human blood.
Esther Blanchett, an orphan raised in the Church of St. Matthias within the city of Istvan, meets Abel Nightroad, a priest dispatched by the Vatican—an ally of humanity—to address threats. Despite his seemingly mild nature, Abel harbors a concealed identity as "The Crusnik," a vampire that preys on other vampires and serves as the Vatican’s ultimate weapon.
Esther's serene existence is shattered when the church faces a bombing, and she is betrayed by her sole confidant, Dietrich. Left with no options, she decides to team up with Abel and Tres Iqus, a humanoid machine, to journey to Rome and discover the truth behind the destruction of her sanctuary. Along their perilous path, they must confront various challenges and delve into the mysteries surrounding Abel's background.