Demon Anime name help

[Kanstanza]

Alright, here goes. I recall this series from a very long time ago, and it's very sketchy, but I wonder if anyone has any recollection at all of what it might be.

Here's what I recall. I'm almost certain that it had to do with demon slaying, protecting the world, yadda yadda, and in it, a girl is given the power to summon up a demon, who, in the series, appears about the age and size of a young boy. He was, if I remember right, a pain in the ass and would flick boogers at the girl.

I only recall that at certain points, he would stop being a little kid and become an actual demon when the time to fight came around. Phsyically, I think he had red/purple hair, fangs of course, and I believe he and his human Master (the girl) were connected via some kind of an arm band. It really has been so many years since I've seen this, that that is all I can remember. I hope someone can help, based off of so little.

[Duuz]

Zenki I believe is it's name. Sounds like it, I never did get very far in that series.