Zihao, who is a fisherman, lives in a seaside town called Guigang, and makes a living on the sea. One day, he meets a mysterious girl called Xiaoyi by accident, and then he starts taking care of her. "Ocean," the fishing ship that Zihao's father has been working on, comes back, but all seamen on it are not there. Under the care of Xiaoyi, Zihao recovers from the sadness of losing his father, and they fall in love. But the happy time doesn't last long. A mysterious middle-aged man called Jin comes to Guigang, and reveals Xiaoyi's real identity, that is, a mermaid. Can Zihao accept it? Can Xiaoyi keep the secret of her population?