Long ago, there was a mermaid princess named Lara, raised with love by her father, the sea king, and her sisters. One day, she fell in love with a human prince on land, a forbidden romance in the mermaid world. Despite the risks, Lara ventured to the surface and, with a potion from the witch Grace, became human. However, the potion had a price—if she failed to find true love, she would turn to foam and disappear into the ocean. Choosing love over her royal status, Lara's wish went unfulfilled, and she vanished into the sea. Two hundred years later, Lara awakens in Lake Biwa, ready to search for her true love.