Seo Dae-young Male 33 years old Master Sergeant, Special Forces Blood Type: B (RH+) Call Sign: Wolf Service Number: 02-241543 Deputy Team Leader of Alpha Team (Mouru Company, Taebaek Division) He is in a relationship with Myeong-ju, but her father, Commander Yoon Gil-jun, opposed them, leading to repeated breakups. While deployed, he and Yoo Si-jin were captured and presumed dead. However, with the help of North Korean Senior Lieutenant Ahn Jung-joon, he returned home, and Myeong-ju's father finally gave his blessing for their relationship and marriage. He has now been married to Myeong-ju for 5 years.

Kang Mo-yeon Female 33 years old Call Sign: Beauty Blood Type: O Professor in charge of the VIP ward, Cardiothoracic Surgeon Currently running a clinic in Gangnam-gu, Seoul. While working as usual, she encountered a patient named Kim Ki-bum, who had stolen Dae-young's phone. When Dae-young and Si-jin came to retrieve the phone, she mistook them for gangsters and reported them to the police. Si-jin took the phone and explained the situation. While treating Si-jin's wounds, they fell for each other and started dating. They broke up two or three times, but while they were together, Si-jin was deployed, captured with Dae-young, and presumed dead. Eventually, he returned home with the help of Senior Lieutenant Ahn Jung-joon and reunited with her.

Yoo Si-jin Male 35 years old Service Number: 05-10655 Blood Type: A (RH+) Call Sign: Big Boss Captain, Special Forces Team Leader of Alpha Team, Mouru Company, Taebaek Division. He excels in both academics and athletics. He originally intended to follow his mother's path to become a judge or prosecutor, but his athletic talent led him to follow his father's footsteps into the Military Academy. His father retired as a Command Sergeant Major. He lives by the belief that beauties, the elderly, and children must be protected.

Choi Woo-geun Male Blood Type: O (RH+) Call Sign: Snoopy Rank: Sergeant First Class He is a rigid and loyal soldier who effectively holds the highest position in the unit after Seo Dae-young. He served alongside Captain Yoo and Master Sergeant Seo. When Captain Yoo was relieved of duty and Seo Dae-young was ordered back to Korea, he briefly took command. When Kang Mo-yeon asked where Captain Yoo went, he snapped at her, asking if she hadn't expected the person she insisted on performing surgery would be relieved of duty. After Yoo Si-jin and Seo Dae-young were transferred, he acted as the practical leader of the team, perhaps because Yoon Myeong-ju, though an officer and superior, was a medical officer. In Episode 6, when an earthquake struck, he returned to the main base with Kang Mo-yeon's group (he told them to go back, but since doctors were needed and he couldn't force them, they came together) to manage the solar power plant that had turned into a disaster zone. Even though Kang Mo-yeon never actually forced the surgery, he was displeased when Yoo Si-jin and Kang Mo-yeon's relationship became public knowledge. He worried—based on experience—that if she knew what they really did as soldiers, she'd tell him to transfer or quit. He mentioned his wife runs a shop, earns well, and is very beautiful. He trusts Captain Yoo and Master Sergeant Seo implicitly... He even believed a flimsy lie that no other squad members fell for, losing 20,000 won in a bet. He has lost a total of 40,000 won so far. His call sign is Snoopy (for some reason). He is an expert who can defuse a bomb in one minute. Those who have seen Yoo Si-jin's 15-year military career say he handles bombs better than anyone. It was even said that there has never been a bomb Sergeant First Class Choi couldn't defuse. In Episode 12, when Argus's gang held Kang Mo-yeon hostage, he played a major role in averting the most dizzying moment by removing the bomb vest they put on her and throwing it away. When Seo Dae-young told him to groom himself since he was going home for the first time in six months, he said there was no need to look good because "couples just need to turn the lights off," earning the envy of others. However, when he showed up for drinks after being contacted by Yoo Si-jin and Seo Dae-young during his leave, it seemed like he had a marital spat... apparently, he almost got beaten to death after turning the lights off. In Episode 15, he visited Haesung Hospital to deliver the news of Yoo Si-jin and Seo Dae-young's death to Kang Mo-yeon, along with Yoo Si-jin's final will. In Episode 16, he was overjoyed when Yoo Si-jin and Seo Dae-young returned alive.

Kong Cheol-ho Male 22 years old Rank: Staff Sergeant Communications and Medic for Alpha Team. The youngest member of Alpha Team. Due to his relatively low field experience, he sometimes makes mistakes during operations and gets scolded often. He has a very gentle personality.

Im Gwang-nam Male 26 years old Rank: Sergeant First Class In charge of explosives and firearms in Alpha Team. He loves dramas and never misses a single romance series.