Lucia is the mermaid princess of the North Pacific Ocean, keeper of the pink pearl, and the main character of the story. She goes up to land to search for her pearl which she used to save a boy named Kaito seven years ago. Later in the series, Lucia and Kaito become lovers. She is unaware of the danger in the marine world and of her real mission until she is told of them by her "older sister", Nikora. She is characterized by her simplicity and naïveté, but with having a strong will, typical traits of shōjo manga heroines.