A success-hungry lawyer meets a young sister and brother suffering from domestic abuse and digs into their case.

How can a mermaid from the Joseon era survive in modern-day Seoul? Shim Chung is a mermaid who finds herself transplanted to modern times. She is caught by Heo Joon Jae, a charming but cold con artist who is the doppelgänger for Kim Moon, the son of a nobleman from the Joseon Dynasty. But in the present time, Joon Jae works with Jo Nam Doo, a skilled conman who guides Joon Jae to become a genius scammer. But Joon Jae’s friend, Cha Shi Ah, who works as a researcher at KAIST, may be Chung’s only hope for surviving in her strange new world.

Go Ho is a 29-year-old advertisement contractor who wants success in both her career and romance. Unfortunately, neither seems to be working out particularly well because the only two men in her life are Kang Tae Ho, her short-tempered boss, and Hwang Ji Hoon, her ex-boyfriend. Dealing with their increasingly irritating behavior and her decreasingly abundant time until she hits the “big thirty,” can Go Ho reach for the skies and capture her dreams, or will this starry night end in darkness?