Jin Youngwon was an unregistered sentinel (something like esper) who had not used his powers when he was forced to join a special branch of the military. There he meets Myung Haejun, an A-class guide captain, who had guided him in the past. Youngwon had sworn not to use his sentinel powers again after being traumatized the day they first manifested. But the military higher-ups have ordered Haejun to prepare Youngwon for battle. On one such day, an air raid siren triggers Youngwon’s trauma from seven years ago ...