Secretly Greatly (2013)

Secretly Greatly is a 2013 South Korean action comedy-drama film starring Kim Soo-hyun, Park Ki-woong, and Lee Hyun-woo as North Korean operatives disguised as a rural fool, a rock artist, and a high school student. They blend into small-town life while waiting for orders, until one day, owing to an unexpected power change in the North, their mission is revealed to be an order to commit suicide.

The 5446 Corps of spies were trained by North Korean elite special forces since their adolescence, presumably to achieve the high objective of reconciling Korea. They are sent to South Korea, where they each disguise themselves as an idiot, an aspiring singer, and a high school student. They gradually become acclimated to living as average neighbors in a small town until one day, their normal lives are flipped upside down when a "secret and big" assignment is unexpectedly assigned to them.

Detailed information:

Starring: Kim Soo-Hyun, Park Ki-woong, Lee Hyun-woo

Original release: June 5, 2013

Link to watch: imdb.com/title/tt2967578/