Laura and her friends receive an invitation from the Grand Ocean Kingdom to visit. Arriving there, the girls are welcomed by the Mermaid Queen who congratulates them for their progress as Pretty Cures. The queen also reveals the existence of the Marine Kuru Ring. While trying to find it while Kururun stumbles upon a dark room. When the Mermaid Queen attempts to take back the Tropical Pacts, Kururun exposes Elda, Chongire and Numeri who reveal they have captured the queen and were using a memory machine to lure the Cure into a trap. The angered girls transform to engage the foe who respond with making a Chou Zettai Yaraneeda out of an octopus...