Doraemon: Nobita no Takarajima

Finding a treasure is always been so hard! But, nothing is ever impossible for Doraemon and his magic tool. And so, with the help of Doraemon, Nobita and the rest of the gang set sail on a ship to find treasure on an islands. However on their way to the island, the ships have almost been destroyed and resulting Nobita to stray on an island with a young pirate while Doraemon and the rest of the gang somehow involved in a war between pirates.And so, their adventure begins...

The plot revolves around a summer vacation of Nobita and his friends under the waters of Pacific Ocean. Jaian and Suneo take Doraemon's underwater vehicle and travel through the Atlantic Ocean, trying to find a treasure ship. Along the way, they discover that the environment gun that Doraemon used to protect them is running out of energy leaving them vulnerable to the sea. Fortunately, they are rescued by some marine creatures. Doraemon and his friends are later captured by these creatures, revealed to be inhabinats of the underwater kingdom of Mu. It is revealed that another undersea kingdom, Atlantis, now controlled by robots, was about to destroy the Earth with nuclear weapons after mistaking a volcano eruption for an invasion. With the help of a young boy from Mu, Nobita and his friends attempt to stop the robots, but are all captured. However, when things are at their grimmest, Doraemon's robotic underwater vehicle sacrifices itself to destroy the computer that controlled all the robots and nuclear weapons. After returning to Mu, Doraemon and his friends are hailed as heroes.

As a summer assignment, Nobita has to research the past of his town. Together with Doraemon, they use a gadget called time camera to take photos of the town sights from various time periods. To their great surprise, the last photo they take depicts Japanese folk hero Momotaro pulling a cart laden with treasure. Later, Nobita's mom encounters a foreigner who shows the kids a small picture of a person dressed as samurai. The picture looks almost like a photo, and the person in the picture looks exactly like Momotaro. The foreigner has inherited this picture from his ancestors, and he has come to Japan in order to learn the truth about its origins. Nobita begins to think that Momotaro might have been a real person. In order to solve the mystery, he travels to the past of Japan along with Doraemon, Shizuka, Takeshi and Suneo.

Nobita asks Doraemon to take him somewhere they can dive and as a result the robot-cat uses several gadgets to make it possible for both to able to swim on an imaginary ocean above sea level. Inadvertently a mermaid ends up on Nobita's backyard when they turn off the illusion. Her name is Sophia and she is a princess of an ancient underwater civilization. Doraemon, Nobita, Shizuka, Jyaian, and Suneo quickly become her friends and are invited to visit her homeland. While heading towards the underwater kingdom they find themselves amid a conflict between the mermaids and an opposing tribe that has driven them away from their home planet thousands of years ago. Doraemon, Nobita, and their friends must then aid Sophia find a legendary sword that might bring peace once again to the seas.