Spoiler alert! ↓
Nobita treats Doraemon to dorayaki, a snack that he likes. Nobita asks him to finish off his homework that has been carried over from two to three days. So as not to disturb Doraemon, he sleeps at the corridor outside his room.
Nobita sleeps soundly, oblivious to the events that happened in the room, and wakes up the next day to find the room in a wreckage, and a beaten-up Doraemon, deprived of his sleep finishing Nobita's homework. Nobita travels back in time to find out what happened during his sleep, and learns Doraemon had went to seek himself two hours; four hours; six hours and eight hours into the future for help.
Doraemon is beaten up by his future selves as they were previously, after they finish the homework, and they went back to their original timelines. Pleased that the homework is finally done, he goes to sleep, but is awakened by himself from the past twice, who takes him inside the drawer to finish the same homework. It is then that he realized that he will be taken away for two more times. Afraid, he hides in the wardrobe where Nobita is, but is taken away yet again.
Upon his return from six hours earlier, an angry Doraemon chases after Nobita, in the process running along the corridor where Nobita is still in his sleep. Doraemon from the past finds himself fighting Nobita, and is being charged at. To express his remorse the next day, Nobita treats Doraemon to dorayaki, but Doraemon runs away, thinking that he will be tricked to do homework again.