A scourge has struck vampire society in the form of serial murders. At first glance, the killings seem unrelated, yet every crime scene shares one common element: a card left behind inscribed with "True of Vamp"—the name attributed to the legendary progenitor of all vampires. The Vlad Agency, a clandestine intelligence operation, summons the renowned aristocrat Dali Delico to head the task force investigating these murders. Dali, however, refuses, preferring to devote himself to raising his children. His former colleagues—Gerhard Fra, Henrique Lorca, and Dino Classico—urge him to balance his obligations to the agency with his parental duties. He consents on one condition: the other three men must also look after their children throughout the investigation. Consequently, Dali's estate serves as both a nursery and the operational base for the four noble vampires. Meanwhile, a criminal organization familiar to Dali lurks in the shadows, harboring malicious intentions that threaten to bring about the collapse of the entire vampire society.