Hell Teacher Nube.

Nueno Mesuke, better known as Nube, is a school teacher who does more than just teach. You see, Nube's left hand is a huge, nasty-looking demon's claw. He uses it to get rid of malicious demons, ghosts, spirits and other supernatural beings that are giving his students a hard time. Nube's left hand was normal, until one fateful day when he exorcised an extremely powerful demon from a child. He was outmatched and lost his left hand. The only way to fight it was to let it enter his body. As a result, Nube has a demonic left hand where his own hand used to be. To educate and protect — that is what Jigoku Sensei Nube does.