User blog comment:Water Dragon Slayer/DREAM BATTLE CHRONICLES: THIRD MATCH!/@comment-5598380-20130801012013/@comment-7418318-20130801095429

Then consider this: Most of the time Freed uses his sword to draw runes, but even after losing his sword in his fight with Mirajane he's still able to write the runes for his demon transformation on himself.

Why should it be any different for Yomazu?