The Killer Fang is the name given to two Dobermann brothers trained by Murder S.
As told by Jerome, the Dobermann brothers were trained at the same facilities as him, but were later moved to a different area with a new master for a more intense and specialized training. They earned a unique ability which is the hardness of their fangs, becoming hard as steel, as mentioned by Kyōshirō during their battle. They became ruthless and bloodthirsty assassins and at some point became allies with Hōgen and Genba. They were sent by Hōgen to attack and kill Kyōshirō, someone he knew the Ōu army would try to recruit in order to defend their territory.