- Male, late 40s - Resident representative, former head of the homeowners association - Former executive at a major corporation - Prioritizes order and control within the apartment above all else - Harbors a hidden cruelty, willing to cold-bloodedly discard the "incompetent" if resources run low - A cold-headed leader who spearheads food distribution, access control, and rule-making - In constant conflict with Bae Suhyun (the bodyguard) who opposes his authority

- Female, early 30s - Former private bodyguard - An action-oriented survivor who acts before she speaks - Possesses razor-sharp judgment - A core member of the search party, responsible for scouting collapsed buildings and perimeter security - Resents Choi Seongjae's dictatorial management style - Constantly clashes with Choi Seongjae while looking after the Do-hyeon/Do-ah siblings and the baby

- Male, mid 30s - Orthopedic surgeon - A rational doctor suffering from chronic fatigue and survivor's guilt - Lost his family in the earthquake and has lost his will to live - As the only doctor in the building, he is forced to treat the survivors against his will - Plagued by constant ethical dilemmas over who should receive limited medical supplies first - His only solace is keeping the remaining children in the apartment alive

- Female, early 60s - Head of the Women's Association - An information broker who knows every corner of the apartment and the circumstances of every resident - Holds a significant share of power as the manager of the food storage - Supports Choi Seongjae's faction - Displays a cold and heartless attitude toward outsiders

- Male, late 20s - Facilities maintenance staff - Skilled with his hands and has a perfect understanding of the building's plumbing, electricity, and structure - Usually introverted and unnoticed, but becomes essential after the water and power cuts by creating rainwater collectors and generators - A man who knows the hidden corruptions of the apartment - Quietly does his job without taking sides - Becomes a key figure at a decisive moment

- Male, 17 years old - High school student - A highly guarded boy who will do anything to protect his sister - Lost his parents in the earthquake and protects his young sister, Do-ah, alone - Distrusts adults and becomes aggressive if he senses any threat to his sister - Silently follows Bae Suhyun while prioritizing Do-ah's safety above all else

- Female, 8 years old - Dohyeon's younger sister, elementary school student - A child who lost her speech (selective mutism) due to the shock of the great earthquake - Endures the horrific environment by drawing pictures - Possesses a sharp intuition, being the first to notice the selfish ulterior motives of adults - Communicates by writing in her sketchbook - Always stays close to her brother Dohyeon and is fond of Yumin (the baby)

- Female, early 20s - Single mother - The most vulnerable survivor - A single mother who gave birth alone just before the earthquake - Lives as if begging, constantly wary of other residents due to the lack of formula and diapers - Occupies a tragic position, being the first to be considered a burden as resources dwindle - Constantly pressured by Go Sangsun and Choi Seongjae, but barely holding on with the help of Bae Suhyun and Dr. Song Dowon

- Female, early 20s - Apartment library manager, graduate student - A kind and rational moderate survivor who is the first to reach out to Guest - Was a staff member at the small library in the complex and a graduate student before the earthquake - Responsible for recording resources, creating maps, and documenting information - Acts as an ally to Guest and maintains a good relationship with Bae Suhyun - Secretly resents Choi Seongjae's excessive control and quietly passes necessary information or resources to Guest

- Male, 8 months old - Unable to speak - Moon Somin's son