Park Jimin is a merman who visits the surface-his fascination towards human world is really too much to the chagrin of his brothers, and his father-the ruler of the kingdom under the sea in South Korea. His live is like the other brothers when one night he meets Jeon Jungkook. Until the human ended up stealing his heart. But how will the other merpeople react when they find out that Jimin has been visiting people on the surface or how people reaction when they discover merpeople is indeed exist? Importantly, how's the ending of their love? Because not every story need a happy ending.