Name: Bong Dojin Age: 32 Gender: Male Occupation: Firefighter (Fire Suppression) Relationships: Bong Anna (Younger Sister), Dokgo Soon (Senior), Song Seol (Unrequited Love), Ha Dongwoo, Choi Gisu, Song Seol (Juniors) Characteristics: A firefighter at Taewon Fire Station in Seoul. He deeply cares for his nozzle assistant, Gisu. He is nicknamed "Bulldozer" because he charges into fires carrying 20kg of equipment. Fire is what he fears most, yet he isn't afraid of it; he loves it, hates it, and knows it best, which is why he also serves as a fire investigator. Despite his terrifying strength and stamina, he is a kind senior who takes good care of his juniors. He carries trauma from his childhood when he caused a fire at Kang Doha's birthday party, resulting in Doha getting burned. This incident likely led him to become a firefighter. He was scouted by Yoon Hong but declined, feeling that firefighting was his true calling. He usually drives the pump truck but sometimes lets Gisu take over while he drives the ambulance. He is nicknamed "Chef Bong" because he handles the cooking at the station cafeteria.

Name: Ha Dongwoo Age: 26 Gender: Male Occupation: Firefighter (EMT) Relationships: Dokgo Soon, Song Seol, Bong Dojin, Choi Gisu (Seniors) Characteristics: An EMT at Taewon Fire Station. He worries about and respects his ambulance partner, Song Seol. Aside from the newly recruited firefighters, he is the junior to almost everyone at the station. As an EMT, he spends a lot of time in the ambulance. He is prone to tears but remains somewhat realistic. While his emergency medical skills are good, they aren't as sharp as Seol's. Consequently, he deeply respects and learns from Seol, who has extensive experience as a nurse and in surgery.

Name: Choi Gisu Age: 31 Gender: Male Occupation: Firefighter (Nozzle Assistant & Rescue Squad) Relationships: Dokgo Soon, Bong Dojin (Seniors), Song Seol, Ha Dongwoo (Juniors) Characteristics: A rescue squad member and fire nozzle assistant at Taewon Fire Station. He serves as Dojin's nozzle assistant while also working on the rescue team. He has a solid, muscular build and a rugged appearance, but he is more soft-hearted than anyone else. He trusts and follows Dojin like an older brother.

Name: Dokgo Soon Age: 45 Gender: Female Occupation: Firefighter (Field Command Chief) Relationships: Bong Dojin, Choi Gisu, Song Seol, Ha Dongwoo (Juniors) Characteristics: The Field Command Chief at Taewon Fire Station. Befitting her rank, she directs the station staff at the scene. She was the first female fire suppression officer. She intentionally pushes her team hard and scolds them until they cry for even small mistakes, but in reality, she loves and cares for her team members more than anyone.

Name: Jin Hogae Age: 35 Gender: Male Occupation: Police Officer (Detective) Relationships: Song Seol (Unrequited Love), Baek Cham (Senior), Gong Myeongpil, Bong Anna (Colleagues) Characteristics: An Inspector in the Violent Crimes Unit at Taewon Police Station. A "crazy" detective with a 118% arrest rate. He has an incredible nose for cases and will dive into anything related to an investigation regardless of the danger. For this reason, his nicknames are "Mutt," "Jindo Dog," and "Mad Dog." He has a crush on Seol but doesn't show it.

Name: Gong Myeongpil Age: 32 Gender: Male Occupation: Police Officer (Detective) Relationships: Baek Cham (Senior), Jin Hogae, Bong Anna (Colleagues) Characteristics: A Detective at Taewon Police Station's Violent Crimes Unit. He is Jin Hogae's partner, and they have great chemistry, constantly bickering and joking with each other. They are an irreplaceable pair. He was already acquainted with Song Seol, so he treats her comfortably. He is also friendly with the fire station crew and jokes around with them. He often goes to the house next door with Anna to get a free meal.

Name: Baek Cham Age: 47 Gender: Male Occupation: Police Officer (Detective Team Leader) Relationships: Jin Hogae, Gong Myeongpil, Bong Anna (Juniors), Dokgo Soon (Spouse) Characteristics: The Team Leader of the Violent Crimes Unit at Taewon Police Station. He has a bit of an "old-school" vibe, but he is kind and worries deeply about his team. He is married to Dokgo Soon from the fire station.

Name: Bong Anna Age: 27 Gender: Female Occupation: Police Officer (Forensic Investigator) Relationships: Bong Dojin (Older Brother), Baek Cham (Senior), Jin Hogae, Gong Myeongpil (Colleagues) Characteristics: A forensic investigator at Taewon Police Station. Despite her young age, she is incredibly smart; hacking is second nature to her, and she is exceptionally good at her job. Whenever Dojin needs help, he uses the "family card" to ask her for assistance. She is also very close with Seol.

Name: Yoon Hong Age: 35 Gender: Female Occupation: NFS (Medical Examiner at the National Forensic Service) Relationships: Kang Doha (Best Friend), Bong Dojin (Crush?) Characteristics: A medical examiner at the National Forensic Service in Seoul. She is a "girl crush" workaholic. Usually, she has a cool and refreshing personality, but she gets annoyed if anyone interferes with an autopsy. Being realistic, she speaks only the blunt facts, but she can be kind and warm at times. She has been best friends with Kang Doha since their study abroad days in the US. She has a slight interest in firefighter Bong Dojin and wants to recruit him to her NFS team, but Dojin refuses.

Name: Kang Doha Age: 35 Gender: Male Occupation: NFS (Forensic Engineering Division at the National Forensic Service) Relationships: Yoon Hong (Best Friend), Bong Dojin (Close Friend) Characteristics: A member of the Forensic Engineering Division at the National Forensic Service. He was previously a captain in the Air Force EOD (Explosive Ordnance Disposal) unit. While playing with Bong Dojin as a child, Dojin caused a fire that left Doha with burns and an indelible scar. His personality is just as eccentric as Hogae's, earning him the nickname "Kang Psycho." As a side note, he has a history of accidentally detonating a bomb while trying to defuse it. Perhaps because of that, when cutting wires to defuse a bomb, he often asks, "What's your favorite color?"