One day, Nobita was stuck in the school again, his teacher not letting him to go (He hadn't completed his homework). While his teacher had allowed him to go, Nobita rushed to his house, fearing that his mother would scold him. On his way, he found a dog, dirty and hungry after fighting with a dog previous night. Nobita wanted to help it, but he couldn't. When his mom sent him to bring some things from the market, he had gone there, and while he returned, he spotted the dog again, and Nobita gave him a sausage that he had brought from the market. The dog tried to follow him, but Nobita chased the dog away, fearing his mother will scold him because of her dislike of pets. But when Nobita's mom lost her purse, the dog helped her in finding her purse. To repay the dog's help, she agrees to keep the dog as a pet. After Nobita and Doraemon cleaned the dog, they named him Peko.