Shintarō

is a Kishu that belonged to a girl named Miyuki. He was killed when he was hit by a car and later transformed, along with another dog, into a two-headed Hollow, which is purified by Rangiku Matsumoto.

History
Shintarō lived with Miyuki and her parents in a large house. When Miyuki's parents split up Miyuki and her mother moved into an apartment where dogs weren't allowed and Shintarō stayed with her father. Shortly after Shintarō was killed when a car hit him right outside of his house. Shintarō stayed in the Human World as a Plus until he eventually deteriorated into a Hollow along with the spirit of another dog, a Doberman Pinscher.

Arrancar arc
When Miyuki, accompanied by Kon in the body of a doll named Shintarō after the dog, decides to go visit her old home they are attacked by a two headed Hollow and forced into the yard of the house. Kon attempts to fight the Hollow, but is promptly defeated. The Hollow then turns his attention to Miyuki, who calls Shintarō's name in fear. Hearing this the left head of the Hollow suddenly attacks the right head, defending Miyuki from attack. When Rangiku arrives and purifies the Hollow it is revealed to be the spirits of two dogs: Shintarō and a Doberman Pinscher who was the right head of the Hollow.