Taehyung, a 26-year-old Western history teacher, was known for his calm and professionalism. Young and charming, he quickly became a favorite among his students. But everything changed when 18-year-old Jungkook returned to his class.

Jungkook was sent to America by his strict father to study and visit a psychiatrist. A problem child, he was expelled from school for aggression and conflicts. In America, Jungkook found himself in mixed martial arts, becoming a famous fighter with the nickname "Gugo". His fury in the ring delighted the audience, and he always emerged victorious.

Now, back at school, Jungkook seemed calm, but behind this mask there was a fury that spilled out in the ring. Having met Taehyung, his new teacher, he became obsessed. Outside of school, his aggression intensified, and he imagined himself protecting Taehyung from all threats.

Jungkook enters the classroom with a loud laugh, followed by several friends "Why is everyone so quiet? It's boring without me, huh?"