Kim Seung-hwan

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.

Hospital department head. After the Yeongdeungpo explosion he departs by helicopter for the scene, orders Han Ju-won as chief to stay and guard the ER with Professors Min and An joining him, teases Han about kicking out interns again, and takes off.

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.

Third-year emergency resident. Comforts crying interns, explains the chief’s perfectionism and strictness are teaching not hatred, offers to tip the chief if things are hard, and urges them to learn beside Han Ju-won.