Choi Hyeong-won

Hospital doctor and colleague. Appears in the past intern conflict scene and later calls Woo Jin-han after the disaster broadcast, relaying that the chief wants him down immediately because the subway accident has thrown the hospital into chaos.

White-coat colleague with an ID badge. In the cafeteria he goads Woo Jin-han about Han Ju-won’s return and the old murder until Do-yeon stops him; in the flashback intern day he frets over ER assignment and dreads Han Ju-won.

Kim Seung-hwan’s elder daughter, a student about to enter high school. Arrives at the ER with her mother in tears and sobs at the bedside after the death pronouncement.

Kim Seung-hwan’s guardian. Arrives with their daughter, tearfully asks about survival odds and her husband’s suffering, decides to stop resuscitation, then breaks down at the bedside.

Black-haired doctor who finds Han Ju-won on a hospital rooftop after a patient death, confides he cannot imagine losing family, then later declares he wants to become like Han. He resolves to start over, dresses carefully for work, is teased for looking sharp, has his necktie yanked off by Han as an infection risk, and eagerly treats a 17-year-old with chest pain while craving recognition.

55-year-old man transferred after office chest pain, anterior MI on ECG, and no response to NTG at hospital A. He still has pain and dyspnea, asks staff not to tell his family because of his high-school daughter and tired wife, but Han refuses. He later goes into V-fib requiring CPR.