'Angel-Devil' That's what they're known as. A gang that consisted of five good-looking high school students who spent all of their time fighting, racing, and clubbing. The member is Do Myung Sik (Lee Kwang Soo). He looks easygoing on the outside, loves to laugh and make people laugh, but when he is going mad he will be very frightening. The next member is Kang Dae Jun (Kim Myung Soo), who can kill and catch all of a girl's hearts with his sharp but handsome eyes. He is very rude and good at fighting, but he has a nice voice and loves to sing. There is also Lee Hyun Ki (Ahn Jae Hyun), he has a very good intellect and always keeps calm with everything, but once people make him mad, he will never let them go and hit them until they collapse. The next is Han Joon Woo. He has a good background as a fighter and has won many battles. Some rumors say that he still has a close relationship with a big Japanese gang, Yakuza, in his family. He can defeat three people at once. But the most dangerous member, who is also the leader of the "angel-devil", is Song Hyang (Song Ji Hyo), the only girl. She beat out Joon Woo  at the battle when they were children, and she also has a black record in the past when she killed someone when she was still a student at primary school. 

On the other hand, Kim Shin (Kim Jong Kook), the ex-fighter who was once a detective, is now in the middle of an investigation into the criminal case that caused many people to die by the "ghost" gang that is still hiding, ACO. Someday, he has a fortune to find the next target of ACO when he does his investigation. Because of the discovery, Kim Shin has to pretend to be a high school student to protect the gang leader Song Hyang, who will be the next target of ACO. He has to face so many difficulties to keep close with Song Hyang so he can prevent her from being killed by ACO and lure the gang to catch them.