Ochikobore Eji Minarai no Shounen. (Jitsu wa) Saikyou Saiaku no Asashin.落ちこぼれ衛士見習いの少年。(実は)最強最悪の暗殺者。; The Lazy Boy is, In Fact, the Strongest and Most Brutal Assassin.

In a certain kingdoms capital, war is approaching. A young boy named Il, an apprentice guard, is treated as a useless person who cant do his job properly, living a lazy life while constantly relying on his stepsister. Amidst this, a certain rumor is spreading throughout the city. It is said that a mysterious group of assassins known as the Night Dwellers are operating in the shadows. This is the story of the worst assassin among them.