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.
Nobita and friends discover an underground cavern that Doraemon has secretly transformed into a hideout, but their exploration goes wrong when Suneo vanishes without a trace. The cave entrance collapses before they can search properly, forcing the group to locate an alternative route deeper underground. What they find instead is something far stranger: a thriving civilization of intelligent dinosaurs who've evolved in complete isolation beneath the Earth's surface. A soldier named Vanho initially appears to help them locate Suneo, but the group quickly realizes the dinosaur society has sinister intentions. They're not interested in peaceful contact. Instead, they view Doraemon and his companions as valuable specimens for study, part of a larger strategy to eventually invade and conquer the surface world. Now Nobita must rally his friends to outsmart their hosts and escape before becoming permanent residents of this subterranean kingdom. The film balances genuine adventure with lighthearted comedy, mixing the wonder of discovering an impossible world with the tension of being trapped in someone else's territory. It's perfect for viewers who enjoy Doraemon's blend of whimsy and action.