Kang Bok-Su was once a misunderstood high school troublemaker, but behind his reckless image was a loyal heart—especially toward his first love, Son Soo-Jung, and his insecure friend, Oh Se-Ho. Everything fell apart when Se-Ho, consumed by jealousy, framed Bok-Su for a violent incident that led to his expulsion. Betrayed, Bok-Su disappeared from their lives, only to resurface years later as a drifting adult working odd jobs. A chance encounter with Soo-Jung, now a teacher, and a media-covered act of heroism pull him back into the spotlight—and into the halls of Sulsong High, this time with a mission for revenge. But returning to school isn’t as simple as Bok-Su imagined. Confronted with Soo-Jung’s conflicted feelings and Se-Ho’s now-powerful role as school director, old wounds resurface. As Bok-Su connects with students and uncovers the corrupt system they’re trapped in, his motives shift. Revenge gives way to a deeper purpose as he fights to protect those who can’t stand up for themselves, including the people who once turned their backs on him.