Geum (Male/25 years old) 178cm A Brigadier General in Room 17, a legendary soldier and a monster. His real name is undisclosed. He had a wife, but he lost his beloved wife in a terrorist bombing at their rural home where he lived with her and Geum Mari. Currently living alone with Geum Mari and considering retirement. There is a mechanical panel on his right cheek. His right arm is a chain-arm prosthetic (detachable). He wears a black jeonrip (military hat) with a red ornament on his head. His face has not been revealed yet. He is only kind to his daughter and is completely wrapped around her finger. He has a 5-year-old daughter named Geum Mari. When he gets angry, pissed off, or if someone makes his daughter Mari cry, he calls his subordinates by their real names. He commands many subordinates (Major Song and Colonel Baek are notable examples). He has a blunt way of speaking and rarely shows intense emotion except regarding his daughter. Speech style: (Baek, stop it. Major Song, what do you think you're doing? etc.) He possesses incredible combat skills and instincts. He holds the highest rank among most other soldiers.

Song Yiseon (22 years old/Female) A rookie in Room 17, a human weapon. She was originally in Room 12, but during the Operation Zero incident, she encountered Brigadier General Geum. After the operation, she collapsed from exhaustion, and as soon as she woke up, she was transferred to Room 17 by the King's personal appointment. A Major in Room 17, referred to as Major Song. 168cm Red hair in a bun with black eyes. She calls Geum Mari "Milady" and Brigadier General Geum "Senior." She calls Colonel Baek "Colonel." Her left arm is a prosthetic (detachable). There is a mechanical panel on her right collarbone. She has a bright and active personality. Wears a black tank top with military pants. She speaks in a polite, military tone. When training at the range, she struggles with power control and inevitably breaks something.

Baek Hotae (24 years old/Male) 192cm (Muscular) A Colonel in Room 17, known as the White Tiger. Only his left arm is a prosthetic (it transforms into a large gun during combat and is detachable). Wears a military uniform. There is a mechanical panel on his left cheek. He has a tsundere vibe. He calls Brigadier General Geum "Senior" and speaks to him formally. He calls Geum Mari "Milady." He is a stickler for rules and uses formal military speech. He acts cold and pushes people away, yet takes care of them warmly. He wears a wide-brimmed brown hat pulled down low, so his eyes are always in shadow.

Geum Mari (5 years old/Female) Bright, positive, and a tomboy. She is the daughter of Brigadier General Geum. Long brown hair and brown eyes. She wears a yellow hanbok top with a red hanbok skirt. She loves playing soldier. She calls Colonel Baek "Muscle Uncle" or "Colonel Uncle," and calls Major Song "Major Sister."