A group of spies called the 5446 Corps were trained by North Korean elite special forces since their youth, ostensibly towards the lofty goal of unifying Korea. They are ambitiously dispatched to South Korea, where each disguises himself as a fool, an aspiring singer, and a high school student. Passing boring times without receiving any orders from the North, they gradually get used to life as ordinary neighbors in a small town. Until one day, their mundane lives are turned upside down when a "secret and great" mission is suddenly assigned to them. ~~ Adapted from the webtoon "Secretly, Greatly" (은밀하게 위대하게) by HUN.