A boy, his father, and his grandfather are stranded in an island after their boat is crushed by a storm. The boy's grandfather sees a spaceship ordering him to leave as there will be a storm that will flood the island. That night, a storm does indeed come and floods the island.
While studying about types of cloud, Nobita asks if there is Heaven in one of them, causing him to be ridiculed by everyone in the school. He resorts to find Heaven on his own when Doraemon initially rejects his pleas, though Doraemon later insists that they should build their own artificial "Heaven". Using Doraemon's gadgets, they solidify a large area of clouds, build an environment on it, and create several cloud-shaped robots for help. They initially keep secret of it by using an invisible dome to disguise the cloud, but later tell it to Gian, Suneo, and Shizuka when they have to invest more money to build a huge castle and create buildings. With shares from Suneo (who invested the most), they manage to transform the area into a large kingdom with various facilities of their interest. Meanwhile, various nature areas in the world, such as the Amazon rainforest are reported to have been stolen by a cloud. As the news reach Nobita and his friends, the city cloud hits a high mountain. Doraemon and Nobita head down to check and find the boy seen in the beginning of the film, unconscious while riding a Crypthodon. They save the boy, but are puzzled by his and theCrypthodon's appearance. The next day, Nobita is crowned the king and wears a special crown which causes everyone in the city cloud to bow down to him, which he uses to stop Gian and Suneo from fighting, but later learns that the boy had disappeared. They head down to try to find the Crypthodon, but winds up arriving at a mysterious land inside a cloud.
