Cha Hyun is a withdrawn high school student who spends his days locked in his room playing video games. But after losing his entire family in a tragic car accident, he is forced to abandon his home and carefree lifestyle, moving into a new apartment entirely on his own. However, his annoying neighbors and financial struggles soon become the least of his concerns as people around him suddenly begin transforming into terrifying monsters, plunging the world into apocalyptic chaos. The situation deteriorates when Hyun realizes that he himself is slowly turning into a monster, while a mysterious voice in his head grows increasingly loud. With time running out, Hyun must cooperate with his fellow tenants to uncover the cause of the outbreak and find a way to survive in this hopeless new world, all while fighting to retain his humanity.