Princess Purple's secret identity is endangered, she transforms into a human while the other princesses face challenges.

The land school challenge of lovely mermaid princesses in the sea. Purple, the mermaid in the sea kingdom, secretly goes on a land tour and is in danger of revealing its identity to humans. At the moment Purple asks for help to the sleeping bubblegem's, Guardian Fairy. The guardian of Bubblegem transforms Purple into a human being. However, due to the excessive use of magic, bubblegem was cut into pieces and scattered on land. Whitegold, the queen who rules the sea, orders the seven mermaid princesses who live in the sea kingdom to attend schools on land and collect all the scattered Bubblegem. Meanwhile, deep under the sea, a sea witch takes advantage of this opportunity to send her men to land to take away the Bubblegem. Can seven mermaid princesses who grew up only under the sea apply well to school life on land? And can they defeat the sea witch's obstruction and collect all the scattered Bubblegem? The rainbow-colored exciting adventure of the seven princesses begins.