When Nobita goes diving with Doraemon, a mermaid named Sophia comes close to him and they all befriend her. When they proceed towards her kingdom, they encounter a fight between two opposing tribes.
Doraemon and Nobita discover a mysterious golden ring far beneath the ice in Antarctica, leading them to uncover an ancient, ruined city.
When Nobita turned the world into a world with magic with the what-if-telephone-booth-gadget, He and his world needed to defeat the threat that became reality in this world.
