There is a hidden kingdom hidden throughout space called Sugartopia, which is home to many candy themed animals and people called Sugartopians which all get power from a special item called the Sugar Rush Crystal which is set within the center of the palace. In the neighboring realm, Sour Land the evil ruler, Queen Acide then dicovered the Sugar Rush Heart and sent monster to steal it, so the ruler, Princess Parfait sent her loyal guards Cure Licorice and Cure Caramel to fight it off and keep it safe. But unfortunately Cure Caramel died and Cure Licorice fell to earth. So Princess Parfait sent her loyal student, Cream to go and find the legendary warriors known as Pretty Cure.

Kona is a young mermaid who has a thirst for adventure and exploring unknown areas despite the potential danger of being spotted by a human. The thrill of finding something new keeps her going and she never gives up the opportunity for an adventure. One day while exploring another shipwreck, she finds several mysterious objects and encounters the sea fairy Delphi who comes from another world called the Ocean Kingdom. Delphi tells her that the Kingdom was taken over and destroyed because a group of evil, corrupted sirens who have now turned their sights on conquering the human world as well. Delphi tells Kona that she is on a quest given to her by the prince of the Ocean Kingdom to find the legendary warriors known as the Precure as they are the only ones said to have the necessary power to not only protect the human world but to revive the Ocean Kingdom as well. Kona and three humans become the legendary warriors and join Delphi on her quest while discovering themselves and overcoming their own personal issues along the way.

An evil force has come to earth! They are targeting the Oceans and the people who live in them! A fairy from a parallel world of oceans comes to earth to find the legendary Precure Warriors so they won't lose the oceans and the entire earth to this mysterious evil force.

There was a legendary war between the Precures and the new enemies called the Neo Fusion Empire. After the battle, their powers are almost gone as they used most of their powers to defeat them. A year passed, the Neo Fusion Empire have returned to conquer the world once again but there is the new Precure team to stop them by using the powers of their senior Precures to defeat them.