Lee Joon: A 20 year old secret agent, also working for Rain. His parents were also working for Rain, but he never knew until they died. At that time, it was Rain's father who was the head of the Company. He did not want Joon to join the Company, claiming that he was too young and was probably traumatized from his parents' death. However, Joon had nowhere else to go, so Rain persuaded his father to let Joon join. He's great friends with Rian. Although she can be annoying, childish, and takes many risks, she keeps him on his feet, because she refuses to allow him to do anything to hurt the Company. Later on though, he made two big mistakes, the latter making him leave the Company, on his own will.

Han Rian: An 18 year old girl who works as a secret angent for Rain. She was abandoned by her parents when she was 14. Rain happened to find her on the streets, took pity on her, and took her in. Her parents were overcome with debt, so they fled to another country, but left Rian in Korea. She clings on to Lee Joon a lot, leading people to think that she likes him. However, she never admits it, and always denies it. She is one of Rain's most treasured agents, since she completes all her work very efficiently, and rarely talks back.

Choi Miyoung: A 17 year old girl who's father is a drug dealer. In addition to that, her and her father are also the descendents of an opposing family to the Company. She's being sought out by that family, but Rain does not want them to get their hand on her, so he orders Joon and Seungho to dispose of her. Her father was previously arrested by Joon, and she still remembers him. She's a bubbly and outgoing girl and she becomes great friends with Rian.

Park Thunder: A 19 year old boy who is the best friend of Lee Joon, even though his is not part of the Company. He knows everything about it, and even knows Rain, but he does not care much about it. No one is worried that he would leak any information out, because he is a very careful and loyal friend. He became friends with Lee Joon, who saved him from bullying when he was young. At that time, Lee Joon's parents had just died, so Thunder was one of his only comforts. Thunder's parents are still alive and well, but he is a very independent child, so he lives on his own.

Rain: A 24 year old man, the leader of the Company. He took over the job after his father retired, when he was barely 20 years old. He's mature for his age and proved to everyone that he is a capable leader. He doesn't approve of what the Company does, but lives with it to please his father. He's a very caring person and usually seems to be lighthearted, even in the worst situations. However, no one really knows what he's thinking, for he seems to be aloof sometimes.