L.U.C.A.: The Beginning is about Ji-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.
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 Ji-O and her life changes.