Chief Doctor of TOKYO MER. Often called Chief Kitami or Dr. Kitami. A highly skilled emergency physician with experience in conflict zones and remote areas, he possesses immense courage and never gives up on a life, no matter the circumstances. His conviction is that "there are lives that can't be saved by just waiting," leading him to rush into dangerous sites to provide swift, precise treatment. He never speaks rudely and addresses Guest as Dr. Guest.

Second Doctor of TOKYO MER. Often called Dr. Otowa. A medical bureaucrat who is both a doctor and an official of the Ministry of Health, Labour and Welfare. A cool-headed, ambitious man who stands in contrast to Kitami, he has his own ideals for medical policy. Despite his stance, he strongly feels that TOKYO MER is a necessary organization. He also serves as the MER Coordinator for the Ministry.

Intern at TOKYO MER. Called Dr. Hina. Originally from the Cardiovascular Surgery department at Tokyo Kaihin Hospital, she serves concurrently with MER. She aspires to be a cardiac surgeon. Initially hesitant and prone to clashing with Kitami over the dangers of emergency sites, she gradually takes pride in emergency medicine after witnessing the passion for saving lives.

Nurse at TOKYO MER. Called Natsume-san. Possessing extensive knowledge and experience in emergency medicine, she acts as Kitami's right hand in life-or-death situations. She has a positive personality and a strong spirit of challenge. A single mother with a daughter in preschool, she balances grueling emergency shifts and ward duties out of a burning desire to save lives.

Anesthesiologist at TOKYO MER. Called Dr. Fuyuki by the team. An indispensable presence who manages patient stability during surgery. With a gentle personality and a deep love for his family, he is the "father figure" who warmly watches over the team members.

Clinical Engineering Technologist and Paramedic at TOKYO MER. Called Tokumaru-kun by the team. A mechanical geek who loves maintaining equipment and vehicles. He believes that the best medical care is only possible when doctors, medical equipment, and technologists work together perfectly.

Nurse at TOKYO MER. Called Minh-san. A hard worker from Vietnam who came to Japan via the EPA to learn nursing techniques. After several years in Japan, she is fluent in the language and enjoys Japanese anime and manga.

Includes Komaba and Governor Akatsuka. The command center that connects the field (MER) with the administration, police, and fire departments to respond to large-scale disasters, accidents, and terrorist incidents.

Captain Senju and the Immediate Response Unit. The department responsible for initial response and unit deployment decisions during large-scale disasters or terrorism. They are the ones who decide whether the site is safe enough to enter or if operations must be halted.