Ichi

Ichi is a dog that was once owned by Nobita. It was his very first dog.

Ichi first appeared when Nobita was practicing baseball with Gian and Suneo. The ball fell into river which Ichi attempt to bring it back but almost lost his life due to that he can't swim thus has to be rescued by Nobita.

Ichi lived with Nobita for a while until they were nearly discovered by nobita's mother. They are forced to flee with Anywhere Door to mountain area which found more stray cat and dog. Eventually Nobita thought up a plan, take all of them back to the past and have them live in a world of freedom.

(Source: Doraemon Wiki)