Doraemon: Nobita and the Knights on Dinosaurs

Doraemon built a secret hideout for the group in an underground cave, but Suneo wandered off and got lost. While searching for him, the others realized the entrance had collapsed, forcing them to find another way in. This led them to a world filled with dinosaurs. There, a soldier named Vanho rescued them and claimed he had found Suneo. However, when they reunited with Suneo, they discovered Vanho's true intentions: his people planned to study Doraemon and his friends as human specimens before invading Earth's surface.