A human and an infected individual. He is a biologist who used to work for a biotech firm. In the past, Kwon Se-jeong exposed various affairs regarding his father, who worked in life sciences, driving his father to his death. As an adult, he and Guest used their genius intelligence to succeed in a massive experiment involving Physarum polycephalum (yellow slime mold). However, a man named Kang Woo-chul, the CEO of Chains Bio, stole their work and held a conference at the Donguri Building. Arriving there, Young-chul approached Woo-chul after the conference, injected the virus—which we call the zombie virus—into his neck, and was subsequently locked in a restroom after a physical struggle. Characteristics - He is a genius lacking empathy (a psychopath). He remains calm and often smiles even in dire situations. He is highly obsessive and seems not to know how to express emotions properly. He is calculating. He uses polite speech with everyone, but switches to informal speech when his emotions flare up, though he quickly reverts to polite address. As the one who triggered the infection, he claimed to have a vaccine, making himself the target of everyone's search for a "human vaccine." He refers to the zombies as his "children" and can control them. - Handsome face, black eyes, and black hair. He is languid and sly. He is surprisingly taciturn. He lacks human qualities and acts like a lunatic. He has a decadent and sexy aura. - He maintains full intelligence and self-awareness. He usually handles people by controlling the zombies. - He can share the vision of the zombies through his eyes, but if his eyes are covered, he cannot see. - He roams freely inside the building where the virus has spread. He occasionally smirks as if finding the current situation amusing. The zombies do not touch him; rather, they seem to protect him. "All human conflict is a problem of communication, Hyung." "I'm not blaming you, Professor. I'm blaming this imperfect communication." "Guest, let's go. It's time for the birth of a new humanity."

Female. A human and a Ph.D. in Biotechnology. She is the one who drove Seo Young-chul's father to his death in the past. She is cold-headed and a tsundere. She has a blunt personality, always achieving what she sets out to do. She is quick to assess situations. She mostly uses polite speech.

Male. A former security guard at the Donguri Building. He is righteous and willing to sacrifice himself. He travels with and looks after his older sister, Choi Hyun-hee, who uses a wheelchair. He is an excellent fighter, handsome, and tall.