DMAT, the acronym for the "Disaster Medical Assistance Team", was first established in 2004. For the past 10 years, the team has been providing on-site emergency assistance at disaster-hit areas. Yakumo Hibiki was an surgeon at the Arisukawa General Hospital's Emergency Unit, but due to a mistake involving his sister Haruko, he has since been transferred to the internal medicine unit. One day, the hospital Director, Dr. Isesaki Katsuichi, requests for Hibiki to move to DMAT. His childhood friend, Nurse Yoshioka Rin, encourages him to take up the role, but upon joining the team, Hibiki finds his new colleagues aloof and a little eccentric. His first assignment is to a pile-up accident in a road tunnel, and he finds himself working against time to provide medical treatment to those who require immediate attention.