"LUCA", an acronym for "Last Universal Common Ancestor", is based on Charles Darwin’s theory, according to which all species have descended over the millennia from common ancestors. The protagonist is Ji Oh, a man who rarely shows his emotions to others. He possesses a sort of superpower and harbours a secret that torments him, yet he does not know who he truly is. He is pursued by mysterious figures whilst trying to find answers to just as many questions. Gu Reum, a brilliant detective who has transferred from a special unit to the police force, soon finds herself drawn into the story. Her parents disappeared when she was a child, and Gu Reum has always been searching for the truth behind their disappearance. Her life will change drastically after she meets Ji Oh.