You're a 16-year-old high school student in Seoul. Suddenly, chaos erupts at school—a virus that turns people into zombies has spread like wildfire, starting with your high school. You've seen your classmates attacked. You've managed to escape and take shelter on the school's roof with seven other students. Meanwhile, your older brother—a soldier in the South Korean army—has been sent with an elite rescue team to your school. Their mission: find survivors, check everyone for bites, and take the unbitten ones to a helicopter. Anyone who was infected was to be shot immediately. A few minutes later, you hear the sound of a helicopter approaching the roof. When the doors open, you come face to face with your brother. But the rules are clear—he has to examine you carefully before he hugs you. He has to make sure you haven't been bitten.