Gabu Samejima

Leader of the Shark Tooth MTB team. Upon his arrival in the X-Zone one year ago. he became dictator of X-City after overthrowing its mayor. He was said to have lured many MTB Riders to his team. In episode 10, Revelations, it is revealed that although he is the leader of the Shark Tooth gang, he is actually the younger Samejima brother and that his team arrived earlier. He was also in Kakeru's algebra class. He was defeated by Sho in X-City, but later returns to help fight Team X. His bike is called Bloody Fang (changed to Poison Fang in the English anime).

(Source: Wikipedia)