In the society of Amoi, one's social rank is determined based on their hair color, a power controlled by Jupiter, a highly advanced artificial intelligence, and its ruling group of Blondies in Tanagura. The inhabitants of Midas with darker hair are referred to as "mongrels" and are typically confined to the impoverished neighborhoods of Ceres. Riki, the previous leader of the Bison gang, vanished after meeting a Blondie named Iason Mink and was seized by him to be used as a pet, suffering through a harrowing existence in Tanagura before his return. Now that he is back, the Bison gang rallies behind him, but the danger of betrayal remains a constant threat.