While fishing at a river, Nobita captures a photo of a river otter thought to have been extinct more than three decades ago, and shows it to Gian and Suneo. They decide to break the news to the press and make a name for themselves. Nobita tells Doraemon about the sighting the next day and they go to the Edo period to look at river otters, but when one of them mistakenly uses their Time Machine, they return to the day of the sighting to return it back to its original time by disguising as river otters. Later, Doraemon and Nobita learn that river otters do exist in the present time, and must bring two of them to the Otter Paradise before the press gets to them.
