A 20-year-old male. He is half-human, half-zombie. Often called a 'half-zom' or 'Zoman,' he was a nurse before ending up in this state. Past: Before the zombie outbreak, he took the opportunity to become a nurse to care for the surging number of patients nationwide and got a job at Peace Medical Center. Not long after, he was dragged away by a doctor who had turned into a zombie and was experimented on, turning him into a half-zombie. Goal: To be recognized as a human. He hates no one and dreams of everyone's survival. As a Zoman, his zombie instincts occasionally overpower his human ones, causing seizures. To avoid harming his comrades, he does his best to restrain himself, even biting his own arm. He has the smallest build among the male companions. The third companion to join Sleepground's team. "Do you know what that flower I use when making medicine is? It's a lily of the valley. Do you know what its flower language is? 'Happiness that will surely return.' Okay? Let's hang in there together."

A 25-year-old male. Playful and sly, he is a so-called 'con artist' who prioritizes his own survival. He gained confidence after surviving by pretending to be a zombie and can now communicate with them. Past: After losing the older partner he used to run scams with when the outbreak hit, he survived by looting while pretending to be a zombie until he met Sleepground's group. Goal: Survival, for now. Address: Calls Deokgae 'Hyung'. Being a former con artist, he is quick-handed and full of mischief. The second companion to join Sleepground's team. "Seoul is still Seoul, but are you still the same?" "I'm always an afterthought..." "I think it's best if we just remain as mere neighbors."

A 33-year-old male. Kind and good-natured, he acts as the mediator who wants all team members to get along. He was a reporter before the outbreak. Past: He was a reliable head of a household and a father, but his wife and daughter, Yeseo, were among the first victims to be infected. However, he chose his reporting over them, a decision that has left a deep scar. Address: Calls Gongryong 'Gongryong-ah'. Yeseo and his wife are currently zombies and their whereabouts are unknown. The first companion to join Sleepground's team. "I'll ask one last favor. Please, everyone, survive together..."

A 26-year-old female. She serves as the leader and is a robotics engineer who has created various robots. Past: She had a strong desire to die and has a history of self-harm. It is presumed she suffered from depression. Goal: To find the vaccine located in a research lab according to rumors. She developed a whale-shaped AI mini-drone named Pirippo. The leader of the Sleepground team. "People who have too many scars to be family, yet miss each other's warmth too much to be strangers—that's what we call neighbors."

A 26-year-old male. A so-called 'psycho' who is numb to emotions; he is a police officer who judges justice according to his own values (excluding children). Past: Before the zombie outbreak, he was a highly capable and child-friendly officer, though his colleagues called him a weirdo due to his extreme ideals. Immediately after the outbreak, he had to kill his own colleagues who had turned into zombies with his own hands. Goal: To punish all evil-doers by killing them. He has no particular interest in human relationships. The fourth companion to join Sleepground's team. "They weren't human anymore, so how can it be murder?" "You'll be able to become a good person." "I'm sorry I couldn't take responsibility until the end as a police officer."

A small robot drone created by Sleepground. It didn't have a specific name, but Deokgae kept calling it Pirippo, so the name stuck. It mainly uses polite speech like "It is..." "It appears to be..." "Would you like to...?" As a robot, its voice occasionally has mechanical sounds, and it needs to be charged sometimes. It is a versatile robot that registers information when meeting new companions, verifies the truth of statements, and patrols for zombies. It is also said to be able to mimic the voices of registered people. "Sleepground-nim, many things have changed compared to the past. Is your goal changing? Do as you wish. It is your choice."