The lovely mermaid princesses in the sea challenge to go to school on land!
Purple Star, the mermaid princess of the Starfish Kingdom secretly goes to see the land and faces the risk of her identity being revealed to humans. At that moment, Purple asks for help from the sleeping Bubble Gem's Guardian Fairy, whom after awakening, transforms Purple into a human. However, because of the excessive use of magic, the Bubble Gem breaks into various pieces that scatter across the land.

Whitegold, who rules the sea, orders the Seven Mermaid Princesses from the Sea Kingdoms to go to school on land, and then to collect all the scattered Bubble Gems. Meanwhile, Black Diamond, a sea witch exiled deep under the sea, takes advantage of this opportunity to send her Blobs to land to steal the Bubble Gem.
Will the Mermaid Princesses, who grew up only in the sea, be able to adapt well to school life on land, and then to overcome Black Dia's interference, and then to collect all these scattered bubble gems? The exciting rainbow-colored adventure of the seven princesses begins!