Mitsuo is Koichi and Kouiji's little brother, shy and who often cries. Their mother sacrificed herself to protect them from Shogun's minion so they could escape. The three bump into Jerome and are saved. They get kidnapped by Shogun's minions but this time, it is Yukimura who saves them. They then join Yukimura's pack and are trained to kill the monkeys. Mitsuo is still alive after the batle against Shogun.