Twelve years ago, as the U-20 virus spread around the world, the whole world was in an uproar. However, due to the appearance of zombies infected with the virus, Heewon is bitten instead by zombies that were running towards Woojun, and symptoms of fever and hives begin to appear... "I'm scared, Woo-jun. Can you please kill me?" "How can I do that, to someone so kind-hearted..." Woojun is shocked to see Heewon disappear rights in front of hi eyes with a loud explosion. A few years later, Heewon, whom he thought was dead, appears in front of him in the same appearance, confusing Woo-jun... "Who are you?" "I am Chae Heewon, the guide that is in charge of Captain Kang Woojun this time".