“LUCA" is based on Charles Darwin’s proposition that all species of life have descended over time from common ancestors. (LUCA stands for "last universal common ancestor.") Ji Oh, who rarely reveals his emotions to others, has a special power and a secret but 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. Gu Reum is a detective whose parents disappeared when she was a young child. When she decides on a course of action, she won't change no matter what. Gu Reum chases after the truth behind her parents' disappearance. She meets Ji Oh and her life changes.