A scourge has descended upon vampire society in the form of serial murders. The killings appear unrelated at first glance, but every crime scene has one thing in common: a card left behind, bearing the words "True of Vamp"—the name given to the legendary progenitor of all vampires.

The Vlad Agency, a secret intelligence operation, summons the renowned aristocrat Dali Delico to lead the task force investigating the murders. However, Dali refuses, choosing to focus on raising his children. His old colleagues—Gerhard Fra, Henrique Lorca, and Dino Classico—plead with him to balance his duty to the agency with child-rearing. He agrees on one condition: the other three men must also care for their children during the investigation.

Dali's estate therefore becomes a nursery and the base of operations for the four noble vampires. Meanwhile, a criminal organization Dali knows all too well lurks in the shadows with evil intentions that threaten to cause the collapse of the entire vampire society.