In January 2013, Jung co-starred in military musical "The Promise". It was co-produced by the Ministry of National Defense and Korea Musical Theatre Association, to commemorate the 60th anniversary of the signing of an armistice. It ran from January 9 to 20 at the National Theater of Korea, co-starring actors Ji Hyun-woo, Kim Mu-yeol; as well as singers Leeteuk of Super Junior, Yoon Hak of Supernova, and Lee Hyun of 8Eight. The musical is centered around a group of soldiers who keeps a promise made to each other during the 6.25 war.