Monsters overtook 80% of the world, and people in Hexaldoria received Classes at birth. Kouji Kagami, a Villager—the weakest Class—reached the unprecedented Level 999. When he met the Demon King's daughter, everything changed.

The Agency centers on Martian, a covert CIA agent who's ordered to abandon his undercover life and return to London station. When the love he left behind reappears, romance reignites. His career, his real identity, and his mission are pitted against his heart; hurling them both into a deadly game of international intrigue and espionage.