Who's That Knocking at My Door, Sir? (2013)

Some North Korean crosses the border of two Koreas as spies, but some crosses it for freedom. JongWon escaped North Korea, but no South Korean troops spotted him. When JongWon reached HakDae and SeungHwan, two South Korean soldiers, they ask him to go back to the North and come back again to hide the fact that they were not guarding the country properly.