Sergeant Jin Young-won, an unregistered special soldier who does not use his Sentinel abilities, is forced to join the special forces when his hidden abilities are discovered. There, Yeongwon meets Captain Myeong Hae-jun, an A-rank guide, who becomes his guide. Yeongwon was intentionally inactive as a Sentinel due to injury since the day his abilities first manifested, but his superiors ordered Haejun to entice Yeongwon into combat. Then one day, the air raid alarm rang and Youngwon had to face the trauma from 7 years ago…