Gōzu

along with his twin brother Meizu were chūnin-level shinobi of Kirigakure before defecting and becoming mercenaries alongside Zabuza Momochi.

Background
He and his brother fled the village with Zabuza Momochi when they failed in their attempt to kill the Mizukage, and thereafter began working for him as assassins.

Personality
In sharp contrast to his brother, Gōzu is described as being rational, level-headed and calm.

Appearance
Gōzu had shoulder-length, wild dark-brown hair and dark eyes. He wears a rebreather that covers the lower half of his face and a large, clawed, poisonous gauntlet on his right arm which had a chain coming out of it that had the other end attached to his brother's own gauntlet. He wore a camouflage suit with bandages around his waist, dark-coloured, knee-length sandals and a ragged black cape. His Kirigakure forehead protector had a single horn on it.

Abilities
Gōzu and Meizu are a paragon of coordination attacking. Gōzu's large metal gauntlets house a retractable shuriken chain running between the two of them, which they can use to bind an enemy and then slice them to pieces. In the event that the shuriken chain is neutralised, Gōzu also has a release mechanism to free him from Meizu for individual attacks. He uses the sharp, poisoned claws on his gauntlet to shred his foes. Gōzu was also skilled in stealth, being able to hide right outside the gates of Konoha without being detected.

Nature Transformation
Gōzu and Meizu have proven skilled in Water Release being capable of appearing out of puddles, hiding in them when needed.

Prologue — Land of Waves
At the start of the series Zabuza sent them to kill Tazuna. Using the Water Release: Hiding in Water Technique to surprise Team Kakashi. With Gōzu immediately launching his brother in front of him the pair are seemingly able to kill Kakashi with ease. As they moved on to attack Naruto Uzumaki, they were stopped by Sasuke Uchiha who broke the chain connecting the two brothers. Still intent on killing them, the brothers separated and attacked the team. They were however stopped by Kakashi Hatake, and it was revealed that he had used the Body Replacement Technique to escape their first attack. Both he and his brother were later tied to a tree so that they can be taken into custody.

Trivia

 * According to the databook(s):
 * Gōzu has completed 313 official missions in total: 71 D-rank, 196 C-rank, 45 B-rank, 1 A-rank, 0 S-rank.
 * In Japanese mythology Gōzu and Meizu are fearsome guardians of the Underworld known more commonly as "Ox-Head" and "Horse-Face".