A kid hatches a dinosaur by accident and has to say goodbye to it, which breaks him just enough to matter. Doraemon's gadgets turn a simple fossil into a full prehistoric adventure where the stakes feel real because Nobita's actually trying to save something he loves, not just win a fight. The movie knows exactly what it is: a story about caring for another living thing, even when keeping it means losing it.

Nobita stumbles upon a fossilized dinosaur egg and decides to hatch it with Doraemon's gadgets. Together they raise the creature that emerges. When keeping the creature becomes impossible, Nobita makes the painful choice to send it back to its own time period in the prehistoric past. But the journey doesn't end there. Hunters from the future are threatening the dinosaurs of that era. Unwilling to abandon the dinosaur to that fate, Nobita, Doraemon and their friends head back through time on a prehistoric adventure to protect the dinosaurs from the hunters. The film pairs time-travel adventure with lighthearted comedy.