Doraemon the Movie: Nobita and the Castle of the Undersea Devil

Synopsis

The story follows Nobita and his friends during a summer vacation spent beneath the waters of the Pacific Ocean. Jaian and Suneo borrow Doraemon's underwater vehicle and travel across the Atlantic Ocean in search of a treasure ship. Along the way, they realize that the environment gun Doraemon used to shield them is running low on power, leaving them defenseless against the sea. Fortunately, they are saved by some marine creatures. Doraemon and his companions are then captured by these creatures, who turn out to be inhabitants of the underwater kingdom of Mu. It is revealed that another undersea kingdom, Atlantis—now under the control of robots—is about to destroy Earth with nuclear weapons, having mistaken a volcanic eruption for an invasion. With the help of a young boy from Mu, Nobita and his friends try to stop the robots, but they are all captured. However, when things seem most hopeless, Doraemon's robotic underwater vehicle sacrifices itself to destroy the computer controlling all the robots and nuclear weapons. After returning to Mu, Doraemon and his friends are celebrated as heroes.