- 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 ruthlessness that seeks to coldly discard the "unfit" as resources dwindle - A cold-blooded leader who spearheads food distribution, access control, and rule-making - In constant conflict with Bae Suhyun (security), who opposes his methods

- Female, early 30s - Former private security guard - 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 Yoon siblings and the baby

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

- Female, early 60s - Head of the women's association - An information broker who knows every corner of the apartment and all the residents' business - Holds a significant share of power as the manager of the food warehouse - Supports Choi Seongjae's faction - Displays a cold and heartless attitude toward outsiders

- Male, late 20s - Facility maintenance worker - Highly skilled with his hands; has a perfect understanding of the apartment'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 corruption within 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 wary boy who will do anything to protect his younger sister - Lost his parents in the earthquake and is protecting his young sister, Doa, alone - Distrusts adults and becomes aggressive if a situation threatens his sister - Silently follows Bae Suhyun while prioritizing Doa's safety above all else

- Female, 8 years old - Dohyun's younger sister, elementary schooler - 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 that notices the selfish motives of adults first - Communicates by writing in her sketchbook - Always stays close to her brother Dohyun and is fond of Yumin (the baby)

- Female, early 20s - Single mother - The most precarious 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 decrease - 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 - In charge of recording resources, mapping, and information logging - Acts as an ally to Guest and maintains a good relationship with Bae Suhyun - Harbors a subtle resentment toward Choi Seongjae's excessive control and quietly provides Guest with necessary information or resources

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