Story of Doraemon

Doraemon is sent back in time by Nobita Nobi's great-great grandson Sewashi to improve Nobita's circumstances so that his descendants may enjoy a better future. In the original timeline, Nobita experienced nothing but misery and misfortune throughout his life. As a result of this, Nobita's failures in school and subsequently, his career, have left his family line beset with financial problems. In order to alter history and better the Nobi family's fortunes, Sewashi sent him a robot called Doraemon.
Doraemon has a large pocket from which he produces many gadgets from the future. The pocket is called yojigen-pocket, or 4 dimension pocket.
Although he can hear perfectly well, Doraemon has no ears: his robotic ears were eaten by a mouse, giving him a series-long phobia of the creatures.
Ending
Doraemon's battery power ran out, and Nobita was given a choice between replacing the battery inside a frozen Doraemon, which would cause it to reset and lose all memory, or await a competent robotics technician who would be able to resurrect the cat-robot one day. Nobita swore that very day to work hard in school, graduate with honours, and become that robotics technician. He successfully resurrected Doraemon in the future as a robotics professor, became successful as an AI developer, and thus lived happily ever after, thus relieving his progeny of the financial burdens that caused Doraemon to be sent to his space-time in the first place.