고애숙/Go Ae Sook (You) - 17 years old

She’s a pretty girl with the occupation as a spy. With her father’s death, she seeks the murderer for vengeance. She transferred to Seoul Arts High School from Seoul Spy Academy. She’s sweet, sensitive, and smart, but cunning and clever. She can also handle any weapon and knows hand-to-hand combat.

김종인 (카이)/Kim Jong In (Kai) - 18 years old

He’s one of the cutest and most popular guys at Seoul Arts High School. Besides his charm and being smart, he hates being the most popular guy in school. When a girl confesses to him or gets near him, he gives them the cold shoulder. Behind his personality, he has a secret of his own.

승명기/Seung Myung Ki - 17 years old

He’s a close friend to Ae Sook that transferred with her to Seoul Arts High School from Seoul Spy Academy. He’s cute and a huge flirt when girls are around. He is also the son of Mr. Seung Kang Dae, the headmaster of the Seoul Spy Academy and the leader of the Seoul Spy Agency.

승강대/Seung Kang Dae - 45 years old

He’s the headmaster of the Seoul Spy Academy and the leader of the Seoul Spy Agency. He was a close friend of Ae Sook’s father during their spy training years.

EXO

They are Kai’s group of friends who are the most popular and cutest guys at Seoul Arts High School. They are like brothers since they have been together their whole life. When one of them is in a rut, they will all help out.