Nora: The Last Chronicle of Devildom(2004)

Nora

When the seal for Nora's form is released he becomes Cerberus, the vicious dog of disaster. But Nora can only use magic when Kazuma grants him permission...and Kazuma doesn't grant permission easily. The Dark Liege wants the two to team up and crack down on renegade demon factions in the human world, but how can they do that if they can't even get along?

(Source: VIZ Media)

Note: Volume 9 includes Special Short Story: Nora! and the one-shot Severer Reito