黑色记事本Milan, 2030; where only eight years earlier the independent global spy agency Citadel was wiped out by Manticore, the powerful enemy syndicate that manipulates the world from the shadows. Since then, Diana Cavalieri (who is an undercover Citadel agent) is alone, trapped behind enemy lines as a mole in Manticore. When Diana finally sees a way out and the chance to disappear forever, her only option is to trust the most unexpected ally, Edo Zani, heir of Manticore Italy, son to the head of the evil syndicate's Italian unit; who just so happens to be vying for Manticore's leadership against other European families.