Doraemon: Nobita and the Dragon Knight

The story begins with Nobita and Xiaofu debating "whether dinosaurs are completely extinct." Since Xiaofu's claim that dinosaurs still exist was completely rejected by Xiaofu in a scientific and reasonable way, Nobita asked Doraemon for help. However, when Nobita asked Doraemon's "OX Divination" tool "whether there are still dinosaurs alive "on earth"", he received a negative answer. Later, in order to hide Nobita's zero-point test paper, Nobita and Doraemon accidentally discovered a spacious underground space using props used to search for underground holes, and built it into a playground for everyone. However, at the same time, Xiaofu was upset because he witnessed dinosaurs one after another in rivers, his own backyard, and underground spaces. The bored Xiaofu went underground again with a camera in order to find out the truth, but lost the trace. Nobita and Doraemon learned from the video taken before Xiaofu disappeared that the location of the underground space was just below the river in the town where everyone lived, so they sneaked in again with Fat Tiger, Shizuka and others, but witnessed an unexpected scene - the ancient jungle of the Mesozoic Era was filled with A wide underground cavity was discovered, and dinosaurs that were supposed to be extinct were also present in it. It turned out that although the OX divination answered the question correctly, it limited the search scope to the "surface" according to the literal meaning of the question, thus covering up the possibility of dinosaurs existing under the surface. Doraemon and his party were captured by the Kappa tribe, a barbarian tribe underground, while they were looking for their husband. When they were facing life-threatening danger, a knight riding a dragon appeared immediately and saved them all. The knight called himself Bach and claimed to be a knight of the underground country. He informed everyone that the above-ground man who looked like the husband had been taken in and protected, and then escorted everyone to the capital of the underground country to meet the husband. During the journey, Doraemon and his party learned that the underground people were a species evolved from dinosaurs and were highly civilized. After reuniting with his husband, Bach agreed to let the group of people return to the surface world safely, but the memories related to the underground world would be erased; but by chance, Nobita discovered that the underground people were secretly planning an operation called the "Great Crusade", and its purpose was to take back the surface world from the people on the surface (human beings)! Unable to sit back and watch this happen, Doraemon and his party had no choice but to escape and fight... Can Doraemon and others escape? Is the war between humans and underground people unstoppable? And what are the real purposes and enemies of the mysterious "Great Crusade"...?