After losing his parents in a tragic plane crash at the age of eight, Ijin Yu becomes stranded in a foreign country with no one to rely on. In order to survive, he is forced to grow up on the battlefield as a child mercenary, learning deadly combat skills far beyond his years. A decade later, Ijin finally returns to South Korea and reunites with the family he thought he had lost. Compared to the brutal life he once endured, his new environment seems peaceful, filled with ordinary comforts like school, food, and a safe home.

However, adapting to normal teenage life proves far more difficult than expected. With only one year of high school remaining, Ijin must navigate friendships, bullies, and the complicated social world of students while hiding the dangerous instincts he developed during years of war. Though high school may appear harmless compared to a battlefield, Ijin quickly discovers it comes with its own challenges. The real question is not whether he can survive school life—but whether the school itself can handle someone like him.