Dong-ho is ranked number 1 in "Arena," an illegal gambling league for teens, but he steps down to prepare for college. However, the members of "Arena" don't want to lose their biggest money-maker, so they place a debt on his brother Dong-min. Dong-min literally fights against his debt, but when he gets hurt, Dong-ho decides to fight back.

6 young girls and boys reveal their most thrilling moment; college student Ji-hoon plays drinking bout with his female friends. Dong-geon's first experience at emergency stairs. Young-jae bets on undressing while playing Jenga with his sister's friend. Young-tak visits his girlfriend's house while her parents are out. Jung-woo decides to go to Motel with his old female friend. Jin-seok goes to theater with his tutor, but it's not to watch a movie.