Zi O (Kim Rae-won) has a special power and a secret, but he doesn't know who he really is. He is chased by mysterious figures, while he tries to find answers to numerous questions that surround him.
Ha Neul-ae-goo-reum (Lee Da-hee) is a detective. When she decides on a course of action, she won't change no matter what. Her parents disappeared when she was only a young child. Goo-reum chases after the truth behind her parents' disappearance. She meets Zi O and her life changes.
A man who has a secret power and is wanted by Human Tech. He doesn't remember anything after waking up from a major happening. He decides to find out who he really is after being chased by unknown people, while understanding that he is not a normal person.
A detective in the Violent Crimes unit 1st team in Juan Metropolitan Police Station. She was originally from the Major Crimes unit, but was demoted. Her parents went missing when she was a kid, and for nine years she never stops finding them.
A former Special Forces soldier. He was sentenced to life imprisonment for having accidentally killed 9 people during a tactical training, when he threw a grenade instead of a flare. He was offered by Cheol-soo to work for him, and lead a chasing team to capture Zi O. He had lost his entire right arm in a past attempt to capture Zi O, and Human Tech had to install an artificial one for him.
A secret influential figure from the National Intelligence Service. He supports Joong-kwon and the project in order to get very rich if it succeeds, and will do anything in order to make the project successful.
The director of Human Tech, and is the scientist who oversaw the only success in the project. In the past, he was forced out of the academia for defying the research ethics of "artificial human enhancement". He was subsequently imprisoned for embezzlement of research funds. After that, Cheol-soo supported him in order for the latter to create the most perfect human being.
The founder of Human Tech. She is the leader of a cult, but believes in scientific theories rather than the words of God. She is well-connected and rich, but doesn't know what she can use them for, until she found her target in creating new lives.
Team leader of the Violent Crimes unit 1st team. He ranks last in the police station for conviction rate, as he was always given the most difficult cases to handle. He detests Goo-reum at first when she joined his team, but he takes care of her like family.
Hwang Jae-yeol as Kim Yoo-chul
A detective of the Violent Crimes unit 1st team. He believes in Jin-hwan more than anyone else, and takes care of his juniors delicately. He was worried about Goo-reum being persistent in investigating the case surrounding Ji Oh, but he is willing to help her till the end.
Part of Lee Son's chasing team to capture Ji Oh. She was sentenced to life imprisonment for having accidentally killed 5 people during a tactical training, when she fired real bullets instead of blanks, and lost her right foot in the same accident. She was offered by Cheol-soo to work for him under Lee Son.
Part of Lee Son's chasing team to capture Ji Oh. He is a network technician who was discharged due to corruption.
Others
Lee Hae-young as Oh Jong-hwan
A professor working under the National Forensic Service. He was close friends with Joong-kwon in college days, but after the latter crossed the line that scientists should not cross, he led people to force Joong-kwon out of the academia.
Ahn Chang-hwan as Won-yi
Zi O's friend. He was the only person who knew about Zi O's power, and in the past he used it for mischief.
Lee Yong-nyeo as Sister Stella
Kim Hyung-min as Ha Young-jae
Goo-reum's father who is currently missing. The co-founder of Human Tech, and was the co-researcher for the L.U.C.A. Project.
In the table above, the blue numbers represent the lowest ratings and the red numbers represent the highest ratings.
This drama airs on a cable channel/pay TV which normally has a relatively smaller audience compared to free-to-air TV/public broadcasters (KBS, SBS, MBC and EBS).
