Doraemon was sent to the past to change fate

One of the main characters, Nobita Nobi, is a lazy, cowardly boy who does badly in school and is often bullied. His redeeming points - he is loyal and kind-hearted.  Doraemon was sent from the future by Nobita’s great-grandson Sewashi Nobi to try to change Nobita’s life. Sewashi hoped that by changing his great-grandfather’s fate, his life in the 22nd century would also change for the better.