He is a former member of the Kamakura no Kyouken (The Mad Dogs of Kamakura) and the Oni-Baku with his partner Saejima.
Jun Kamata who now lives in the due to a promise which he made while he was growing up. Along with Saejima they were known as the no Kyouken (The Mad Dogs of Kamakura). Before they both joined the Oni-Bake they were the most feared gang, as their vicious attitude and fighting skills were unmatched until they met the Oni-Baku. During when Onizuka and Danma started to become the best gang in Shonan, Jun and Saejima were not impressed and decided to wipe them out. An epic battle begun with Jun Fighting Onizuka, eventually losing to him. After this they both joined the Oni-Baku and fought many other gangs.