Demon of the Hidden Mist.
A simple phrase, yet it struck terror into hardened hearts. The words brought to mind a shadowy figure, cloaked with mist, a massive zanbato held nonchalantly in a ready grip. Death followed in his wake, his kills unable to be accurately tallied.
While not the most powerful of the Kiri Swordsmen, this man elicited the most fear in the shinobi world for events only whispered about. The Kiri Academy Massacre. Disappearance of both of the Fire Daimyo's nephews and their respective entourages with only the kanji 'Demon' painted in ink to hint at what occurred. Countless assassinations across the Hidden Elemental Nations executed without a hitch.
Such a powerful and mysterious figure has nothing to fear many shinobi reasoned, pointing at the lack of any confirmed woundings, or even successful engagements against this Zabuza. However they would be wrong.
Racing down the dank corridors of the Mizukage's palace, hurtling towards his inevitable battle, this dark legend turned and saw the only thing in this cruel world that he still feared for. The young girl he had found huddled on that freezing countryside bridge, his pale apprentice who he silently considered his daughter. The reason for the Demon to assume a noble mantle and stand against his Kage's tyranny.
Haku, the Demon's Ice Angel.