Doraemon Episode 755AB

Doraemon is sent back in time with a young boy named Sewashi Nobi to fix his great-grandfather, Nobita, so that his descendants can enjoy a better future. In the original story, Nobita experienced nothing but misery and misfortune, manifested in the form of bad grades and bullying throughout his life. This situation led to the collapse of his future business which caused him to leave his family, which was also beset with financial problems. In order to change the history of the Nobi family, Sewashi originally wanted to send a "super-robot" to protect Nobita, but with his meager money, he can only afford an imperfect robot that the toy factory rejected: An anthropomorphic robotic cat named Doraemon.