Chibi

was an abandoned dog that Nagato found while wandering around the streets after his parents were killed.

Background
Nagato fell down into the water because of hunger and was dying but thanks to Chibi, Nagato found the will to go on. Then, they were helped by Konan, who gave some bread to Nagato and Chibi. They joined Yahiko and Konan to steal food from various vendors in search of food. Chibi was later killed in the crossfire of Hanzō's battle with the Sannin. The Ame Orphans later mourned his death.

Trivia

 * Chibi means "tiny".