Mamoru Aoyama (青山 まもる, Aoyama Mamoru) was an inmate at the juvenile detention center. Often picked on by the other inmates due to his short stature and feeble nature, he received some training from Danpei, who teaches him dodging techniques that make him a hard opponent to fight against, even managing to score a win against one of the toughest inmates during the juvie boxing tournament.