Doraemon: Nobita and the Kingdom of Clouds

In class, Nobita asks his teacher where heaven is located during a lesson about clouds. When the other students laugh at him, Nobita tries to find proof that a heavenly place exists above the clouds. Doraemon explains that such a place can't exist scientifically, leaving Nobita disappointed. Eventually, Doraemon helps him create their own kingdom in the clouds. But they soon discover that mysterious creatures have been living there all along.