On May 11, BTOB's Sungjae, together with Hyunsik, entered the Army Training Center in Chungnam and bid their temporary farewells to their fans and co-members. They were also greeted by a group of press before enlisting.
Prior to joining the army, Sungjae published a series of new selcas, showing his new haircut. He also wrote a heartfelt letter to Melodys on May 3 wherein he announced his enlistment.