This time, Barbie plays Lumina, a mermaid who wants to see the palace. She has a magical royal power that can make pearls dance and change according to her wishes! Lumina and her little playmate Kuda, a cute pink seahorse, embark on an adventure in the underwater castle. During this time, she helps her friends prepare for the royal ball. Lumina finally saves her aunt, Sheila, with her magic. The king also knows that Lumina is his lost daughter because of her magic. Lumina also learns her true identity and returns to the palace and embraces her parents.