Kim Yewon, goes by her assassin name, Umji, mastered the trickery of hacking. Well, she does killing, rarely. But when she whips out her weapons, you know  is about to go down. She joined a group of underground people so that she can finish what she started on a long time ago.

Hwang Eunbi, who goes undercover by the name of Sinb, has the skill of assassinating and hacking. She does both, depending on her mood. She recently joined the group in order to fufil her dreams. But she found herself getting drowned into the drama with her crush that led to the opening of a dark secret behind their true motive to join this dangerous underground society.