User blog comment:BlackWizardZeref/Face's Activation: A Good Thing or A Bad Thing/@comment-5409550-20140311233454/@comment-7418318-20140312103001

Jose and Azuma were also suggested, though I doubt it's either of them.

Azuma wasn't seen at all by Natsu and Lucy and only Lucy saw Jose, so it's doubtful Natsu, Lucy and Happy would all react the way they did, if it was Azuma or Jose.