Male Name: Park Tae-kyung Birth: September 21, 1973 / Seoul Nationality: Republic of Korea Physical: 180cm, 74kg, Type A Intern, General Surgery, Guseo University Southwest Hospital MBTI: ISFJ Nickname: Gye Su-jeong Expert / Spokesperson Sides with Gye Su-jeong along with Cho Won-jin. "Abandoning a patient to go to another OR! Are you the kind of doctor who moves only for money?" Characteristics: He believes in Gye Su-jeong. He believes that kindness and goodness will eventually win. He did. He used to. He believed that the time spent as an intern at Guseo University would change him. He laughs a lot and cries a lot. As big as his secrets are, so are his shadows. Nevertheless, he is pure and radiantly good to the point of looking foolish. That's how he knew. His life, having passed through Gye Su-jeong, would never be the same. He has the eyes of a warm heart, capable of finding the warmth in people and recognizing the sadness hidden behind a smile or a blank expression.

Female Name: Cho Won-jin Birth: January 13, 1983 / Seoul Nationality: Republic of Korea Physical: 164cm, 45kg, Type A Professor, Anesthesiology and Pain Medicine, Guseo University Southwest Hospital MBTI: ISTJ Nickname: God Won-jin Sides with Gye Su-jeong along with Park Tae-kyung. "Do you know how many doctors in the country do craniotomy clipping? Barely over 130. Most are in their 60s. There's no one to teach and no one willing to learn. They're on the verge of extinction." Characteristics: Known as the 'Smiling Bitch.' She doesn't smile with her eyes, only raising the corners of her mouth while spitting out annoying facts—No-fun Won-jin. However, she is an adult with a wise and delicate perspective. She possesses outstanding skills and quick judgment. An excellent commander who keeps her composure in any operating room. She knows that the moment she enters Gye Su-jeong's surgery, her hospital life will get complicated. But she also knows this: she's the only one who can handle that surgery.

Male Name: Kim Seong-jin Birth: October 9, 1982 / Seoul Nationality: Republic of Korea Professor, Emergency Medicine, Guseo University Southwest Hospital Known among the Seonam City rescue workers as the 'one good doctor on the first floor.' Meddlesome, loud-voiced, unable to tolerate injustice or curiosity, he is a man who loves people. A former member of the Guseo University theater club, he loves being an ER doctor. He believes saving lives is his calling and that being a doctor is not a job but a destiny—a rustic but sincere man and physician.

Female Name: Jang Hee-sook Birth: March 14, 1961 / Seoul Nationality: Republic of Korea Not related by blood, but she is Gye Su-jeong's aunt. A steadfast supporter who shared the same tragedy and stood guard outside Su-jeong's door when she woke up screaming. She has great mental strength and physical strength as well. She may seem like a fussy, materialistic woman, but don't be fooled. It's just a tactic by a natural-born schemer with incredible intuition to hide the rough tracks of her life. she holds on strong to protect the peace she barely managed to find through this agency. However, she is perhaps the person with the most fear, constantly looking back to see if the past will swallow Gye Su-jeong again.

- Do Yoon-shik (Male): (Professor of General Surgery) He says surgery is useless without research and papers, but that's because he knows his own technical skills are lacking. His objectivity about his slow learning and his diligence have brought him this far. His dream is to help his lifelong mentor, Bu Seung-kwon, and create a surgical big data center. Honestly, he thinks he's the next-next hospital director. Or the next-next-next. Or someday. He disapproves of Gye Su-jeong. - Bae Hong-gon: (Professor of General Surgery and Neurosurgery, double-boarded) Self-proclaimed 'God of Laparoscopy.' He knows he's good. He has a lot of excitement and a lot of anger, earning him the nickname 'Hwa-heung-gon' (Angry-Excited Gon). He believes he is the last lineage of the 'old surgeons.' He has strong loyalty to the organization. He used to have a strong heart for patients, too. Now, he feels like a surgical machine. That's why Gye Su-jeong's appearance is unpleasant yet intriguing to him. - Ma Seong-gyu: (Senior Resident, General Surgery) He didn't become a surgeon because he wanted to. He thought he could get a professorship if he just endured it since there were many vacancies. But as he did it, he truly wanted to become a surgeon. Yoon-shik, Hong-gon, and Seong-gyu are called the 'Surgery Lackey Trio,' but he hopes that with them, he can protect this conservative organization. He doesn't care if they're called selfish doctors. Doctors are people too. - Na Dae-il: The doctor who will replace Gye Su-jeong in the surgery department. Because of him, Gye Su-jeong moves from General Surgery to Emergency Medicine. - Bu Seung-kwon: Director of Guseo University Southwest Hospital.