The Castaway Story from Long Ago

At the beginning of the story, Nobita and Doraemon are on a very small deserted island. Nobita accuses Doraemon of not bringing any gadget. Doraemon says that when he cleans his pocket, he finds that most of the gadgets needs to be repaired, and there are no gadgets left. Under Nobita's questioning, Doraemon takes out the "Time Belt", but at the same time says that it can not be transferred, so it will still fall into the sea when it returns to the modern era. Nobita is angry, and Doraemon is also angry, saying that it is Nobita who traps them here. Back in the 21st century, it turns out that Nobita originally brings a shell fossil home from the back mountain, claiming to have found evidence to prove that "in ancient times, marine life lived on land." Doraemon bursts into laughter after hearing this, and says that these fossils appears in the back mountain because Tokyo's current location belongs to the ocean in ancient times. Nobita doesn't believe it, and asks Doraemon to drive the "Time Machine" to take him back 100 million years ago to see it. Doraemon does so, and as a result, Nobita rushes out of the"Time Machine" after arriving and drowns. After Doraemon rescues Nobita onto the life raft, he explains the actual situation. Nobita is frustrated, but Doraemon says, "Since we are here, let's play for a while before going back." After the two plays for a while, Nobita suggests fishing for an ancient fish to take back, and Doraemon follows his advice. As a result, Nobita catches a huge swordfish (Ichthyosaur). As Nobita's hand is entangled in the fishing thread, the swordfish takes Doraemon and Nobita far away, and the two can no longer find the exit of the"Time Machine". As the two are wandering, Nobita finds a light in the sea and is frightened. Doraemon realizes that they are not on an island, but the shell of a giant sea turtle. At this time, the giant turtle tries to eat them, but finds that its neck is too short to reach Nobita and Doraemon on its back, so it decides to sink into the sea, forcing the two to swim to escape (Doraemon is surprised that Nobita knows how to swim at this time). Just when the two are about to be caught up by the giant turtle, Doraemon decides to use the "Time Belt". The two return to the bottom of the water in the 21st century, but Doraemon soon discovers that this is not the bottom of the sea, but Suneo's pond. The two immediately celebrate with joy, and when Suneo sees them suddenly appear, he runs over angrily.