The story revolves around Koyomi Morishita, a clumsy high school freshman girl who is often mistaken for a grade-schooler because of her shortness. Koyomi becomes a disciple of Misa Anehara, a 25-year-old graduate student who happens to be one of the most powerful modern-day magicians.

:As the mermaid princess of the North Pacific (one of the seven mermaid kingdoms), Luchia entrusts a magical pearl to a boy who falls overboard a ship one night. Luchia must travel to the human world to reclaim her pearl and protect the mermaid kingdoms. Using the power of music Luchia is able to protect herself and the mermaid kingdoms from a growing evil force.