YOUR ENEMY IS ALWAYS IN CLOSE PROXIMITY

S1 E6: The brothers secretly collaborate to catch the real killer, "Yoon-jae," and clear Sung-Hoon's name. As they track the killer, a child from Jo Eun-Ki's center, Yuna, is brutally attacked. Sung-Joon identifies the suspect, Choi Soon-Gil, from Yuna's drawing of a tattoo and confronts him, finally uncovering a crucial piece of the puzzle.