Doraemon Movie 13: Nobita and the Kingdom of Clouds

Nobita's curiosity about the existence of heaven is sparked in class when his teacher explains clouds. He's initially dismissed by his classmates, but Doraemon takes an interest in his question and helps him find a scientific explanation. Doraemon then assists Nobita in building a cloud-based kingdom, but they soon discover that they're not alone in their cloudy domain.