Zero is a silver Siberian Wolf. His fur was initially portrayed more silver in color, but is portrayed as bluish after the style change.
As a puppy he is playful, curious, and brave, but also a bit reckless. Now as a 1 year old, Zero determined and strong for a young wolf.
Byakuren No Fang
Zero was originally born in Siberia but was shipped to a pet shop by a group of poachers. He was then bought for Makoto as a present from his father. His father who is a sumo wrestler had spent the price of winning on alcohol, and despite promising Makoto a Tosa puppy he bought a wolf and tried to disguise it as a Tosa.
Then, they come across Unryu and his owners looking for a fight. Zero recklessly attacks the tosa but easily gets defeated and rushed to the hospital with Uminishiki. During his stay in the hospital the doctors discover Makoto's father's ruse.
Despite his father's ruse Makoto decides to keep him. One day, Zero's mother Silver Fang shows up at Zero's new home having traveled all the way to Japan to find her son. Zero went off with his mother but is stopped by Unryu, who kills Zero's mother. After that day, Zero swore revenge and trains with his owner, Makoto, to become a fighting dog in order to defeat her murderer.
During another training run they are ambushed by an owner with a german shepard looking for a fight. But with 30 kilograms of weight added on him, Zero manages to death the dog with his strength impressing everyone.
Together with his master, Zero travels to the old man Furuya Kenichi to get more fighting experience. After a while, he and his master enter a tournament where he has to face Unryū. Zero beats him and has won the first round.
However, he knows that Unryū won't let the defeat pass by easily, so Zero starts to intensify his training. His next match was towards Benigumo, another Tosa raised by Anzai Nosuke. Zero wins this match too, but only barely.
Time passes by and Zero becomes more confident in himself. At the next tournament, he faces the half blind Tosa, Dokuganryū.
Zero's pride quickly brings him into trouble in this match. Only 1 minute into the fight, Dokuganryū takes over and slams Zero to the ground. Zero quickly remembers his training and fights back. He blinds the old dog after smashing him into the bars surrrounding the area. After a hard fight, Zero wins. His next match is with the dog, Ken'ō.
This fight ends shortly after started because both of their training throws the towel in the ring. For the first time, Zero leaves a match without winning but with a new friend instead. Finally, Zero meets Unryū in the final match.
They fight long and intense and Zero is almost killed. In that moment, Zero remembers his mother's death and regains his energy. He defeats Unryū and finally gets his revenge.