Shiroi is a koga dog whose fur was dyed by retarded "scientists" that were trying to make him into a polar bear, but just ended up having a white dog with a gray Mohawk. The "scientists" wanted to name him Shirokuma which ment "White Bear" in Japanese, but they named him Shiroi due to his white fur. The dye seems to have given him brain damage as well, since he's too stupid for his own good.
Shiroi joined the Koga Clan because they reminded him of himself and thanks to that, he got to meet his cousin, Koji, his uncle, Hacker, and Hacker's best friend, Ryouta. But because of him also being in the Ohu Army, he meets the akita, Akizuma whom he befriends, but when he kills Koji, Hacker, and Bemika, he blames the young akita and is seen trying to kill him during most of his appearances due to his grieving. This worries Weed, but he doesn't complain even though he knows Akizuma is as strong as Shiroi. Most of the Ohu soldiers wonder who will win the last fight.
Shiroi and his girlfriend, Haruko, are sexing it up when they run into Crematory and his son, Hairy Tour Guide. Haruko is attacked, but Shiroi is defensive and is ready to fight for Haruko's life, but Crematory does the job resulting in Hairy Tour Guide's death.
One day, he is thrown into a spreading forest fire by Akizuma and he dies quickly. His spirit comes to Haruko's aid when she is almost killed by a boar that attacked Hairy Tour Guide earlier.