Nobita and Doraemon create an imaginary ocean above sea level, allowing them to swim. However, their illusion accidentally brings a mermaid named Sophia, the princess of an ancient underwater civilization, into Nobita's backyard. As friends, they are invited to visit Sophia's homeland, but their journey is disrupted by a conflict between mermaids and an opposing tribe that drove them away from their home planet thousands of years ago.

Doraemon The Movie: Nobita's Great Battle of the Mermaid King
A legendary sword with the power to bring peace to the oceans is the ultimate goal for Doraemon, Nobita, and their friends as they join forces with Sophia to embark on a thrilling adventure.