Lucia nanami, the mermaid princess of the north pacific ocean, sets out to land to find a boy she saved from a tsunami wave seven years before the beginning of the story, the whom she fell in love and had entrusted her pink pearl.

She eventually finds the boy: a surfer named kaito domoto. However, kaito doesn't recognize lucia in her human form. She cannot directly tell kaito who she really is.

otherwise, according to the mermaid legend, she would turn into bubbles. Lucia tries to convince kaito into figuring out who she really is.