Doraemon: Nobita to Kumo no Oukoku

In class, Nobita asks the teacher about the location of heaven after a lesson on clouds. Mocked for his question, Nobita seeks evidence of a paradise in the sky. Doraemon tells him such a place isn't scientifically possible. Feeling disheartened, Nobita is encouraged by Doraemon to build his own cloud kingdom. Unbeknownst to them, beings have already lived on clouds for a long time.