How can a mermaid from the Joseon period adapt to life in contemporary Seoul? Shim Chung, a mermaid, unexpectedly finds herself in the present day. She is discovered by Heo Joon Jae, a suave yet aloof swindler who bears a striking resemblance to Kim Moon, the son of a nobleman from the Joseon era. In today’s world, Joon Jae collaborates with Jo Nam Doo, an expert con artist who mentors him into becoming a master of deception. However, Joon Jae’s acquaintance, Cha Shi Ah, a researcher at KAIST, might be Chung’s only chance to navigate and survive in this unfamiliar environment.