The play tells the story of Lin Weixu, the eldest daughter of the Daqin Kingdom, who encountered a mermaid from the enemy country who was being hunted down and beaten for trying to escape. She kindly rescued him but was unexpectedly relied on. Looking at that beautiful face and blue eyes that had brought disaster to the country and the people, she suddenly had a perverse idea to raise him in her own house. From then on, an ambiguous and extreme tug-of-war began... The series is adapted from the novel "My Mermaid Brother Bit Me Again" written by Mu Touxi.