A lost friend becomes the thread that pulls you into a world where dinosaurs are real and the people who live there aren't just hostile, they're methodical about it. Doraemon's gadget solutions stop working the way you expect them to once the stakes become about survival instead of problem-solving. The movie trades the comfort of the TV show's reset button for something sharper: a threat that doesn't care about your gimmicks, and a rescue mission that keeps spiraling into something bigger every time you think you've found the answer. It's the moment when Nobita realizes he can't just call home to fix this. What starts as "find Suneo" becomes a question of whether any of them leave that world the same.

Doraemon builds a hideout for the gang inside an underground cave, but when everyone comes back out, Suneo is missing. By the time they realize he is lost, the entrance has been destroyed, so the group has to find another way into the caves. Their search leads them into a world of dinosaurs. There a soldier named Vanho rescues them and tells them he has found Suneo. Once they are reunited, they learn what Vanho's people are planning: to study Doraemon and his friends as human specimens and to seize the surface of the Earth. The film is a fantasy adventure with plenty of comedy mixed in.