The unnamed owner of GB was shown in a flashback at the beginning of the manga where GB used to live in a happy life as a pet dog. However, the happy life was shattered when the owner was involved in the money debt and he tearfully chased his dog away by lashing him with a leash before hanging himself. Then, when GB came back and found his body, the ambulance had also arrived and took the body away that GB chased after the ambulance without realizing that there are other vehicles on the road which caused the dog to almost get run over on the road if not for Smith's intervention (which saved GB's life and had cost Smith's leg).

In the anime, he died of an unknown cause before the beginning of the series so he is only mentioned.