In the suburbs of Tokyo some time ago, there lived a clumsy boy about 10 years old. There appeared in front of him named Sewashi, Nobita’s descendant of four generations later from the 22nd century, and Doraemon, a 22nd century cat-type caretaker robot who helps people with its secret gadgets. Sewashi claims that his family is suffering from the debts Nobita made even to his generation, so in order to change this disastrous future, he brought along Doraemon as Nobita’s caretaker to bring happiness to his future, although Doraemon is not happy about this. And so Sewashi installed an accomplishment program into Doraemon forcing him to take care of Nobita. Unless he makes Nobita happy, Doraemon can no longer go back to the 22nd century. This is how the life of Doraemon and Nobita begins. Will Doraemon succeed this mission and return to the 22nd century?

When Nobita feels like diving in his hometown, Doraemon uses a Underwater Pump Simulator to pump all the water out of Tokyo, causing the entire city to go underwater. That night, Doraemon and Nobita use a Diving Mask Simulator to dive underwater. Later on, lots of fish, and a shark attack Doraemon and Nobita. So, Doraemon puts a stop on the Underwater Pump Simulator, but there is a girl named Sophia, lying down on the bushes in his neighborhood.