Puppy (子犬, Koinu) is the pet puppy of Sakura Sakurakouji and is the offspring of Dog, who had been killed in the first episode.
Puppy is the child of Dog, a dog Sakura fed at the beginning of the series after the homeless man taking care of her was killed by G-Falcon. After Dog was killed, Ogami found and gave Puppy to Sakura.
Five years later, Puppy, now a full-grown dog, is seen with two puppies of his own. He seems to notice Ogami, who was listening to Sakura while hiding behind a tree, whereas she doesn't notice the presence of the Code:Breakers at all.