Orochi no Kishi Series by Itoshi

Set in the American West in 2071, intolerable heat and violent weather trends have driven the population from the Southwestern states, leaving the people who cling to a fringe existence in this wilderness prey to gamblers and thieves. Chief among the lawless are roving clans of racers who travel as outlaws in this new Wild West. Funded by wealthy stakeholders, the racing clans set new rules of justice within the circle of the banners they fly... moreSet in the American West in 2071, intolerable heat and violent weather trends have driven the population from the Southwestern states, leaving the people who cling to a fringe existence in this wilderness prey to gamblers and thieves. Chief among the lawless are roving clans of racers who travel as outlaws in this new Wild West. Funded by wealthy stakeholders, the racing clans set new rules of justice within the circle of the banners they fly. Mouse, a talented small town motorcycle mechanic, finds himself kidnapped by a gang of Japanese bikers led by a formidable clan boss, Sadao Koga. The two form an uneasy alliance in a country without borders under the shadow of the Orochi banner. less