A 30-year-old teacher at a private school in Seoul falls in love with a teenage student in one of her night classes.

Sang-ho is an ordinary high school student. His dream is to enter the military academy under the influence of his father who is an army colonel. As entering high school, he became friends with Jae-gu, Chang-bae, Kyung-chul, Hong-kyu and Sang-sik. They grouped a soccer team called 'Tiger', building up friendship by playing soccer. Sang-ho and his friends ran into group of fight with seniors, these incidents made everybody in school to misunderstand them as they were serious group of gangster. When Sang-ho gets becomes close with a girl whose boyfriend is a boss of another school's gangster group, things are going worse.