Zero is the younger brother of Ziggy and the deuteragonist of the game. He was named Z.E.R.O as a machine by Ziggy.
Like his older brother, he has the same hair color and eye color. He is dressed in a similar outfit to Ziggy's but wears a purple shirt with a similar banner and wears gloves. He wears shorts, shoes, earbuds, and a purple veil accessory.
As a machine, his hair is rose colored instead of white. His hair is more spikier and wears a white skull shaped mask with pink glowing eyes. He wears a red suit with goggles, spiked boots, and some jet pack accessory.
In the beginning of the story, he and his older brother Ziggy tried to flee to the desert from a group of machines called the Mechanical Militia. However, two stargazer named Fullhouse and Number. 42 caught them both. Full House takes Zero away and is about to kill Ziggy when the Soul Master appears. He uses Ziggy's cube pendant to summon Her Majesty, a soldier-type Tune Trooper. The Soul Master and the Tune Trooper defeat the robots and drive Number 42 and Full House away. After 5 years of training, Ziggy starts his quest to find his little brother.
Ziggy found a robot who deserted the Mechanical Militia and named the machine Z.E.R.O., due to the large number of zeros in his name. It is noted that the cube pendant resonates when they first meet. He then travels to Full House's tower, where he defeats Full House and rescues Golden Wing, a Superstar who joins Ziggy's party.
Once Ziggy reaches the core system, he finds that Z.E.R.O. is not a deserter and has been working for Number 42 all along. Z.E.R.O. leads the party to the final confrontation with Number 42, when he steals the cube pendant, allowing Number 42 to use its power to activate the Network, a collective consciousness which can take control of all living beings in the land of Melodica. Ziggy then proceeds to fight Z.E.R.O.. Ziggy disables Z.E.R.O., and when he is remade by Number 42, the Song of the Unsung is unlocked from Ziggy's pendant. The Song of the Unsung is a song made by conductors of old that disables robots when used. Once Number 42 realizes that he has been betrayed by Z.E.R.O., he unleashes all four Stargazers, and they attack Ziggy. After the battle, Number 42 has merged with the Network, transforming into Ultimate Answer 42 and granting him near invulnerability. Z.E.R.O. uses himself to channel the Song of the Unsung into the Network to make Ultimate Answer 42 vulnerable. While this is happening, Z.E.R.O.'s faceplate shatters and it is revealed that he is really Zero, Ziggy's lost brother. After Number 42 is killed, Zero sacrifices himself to destroy the Core of the Network for good by channeling his current into the Core. The resulting explosion leaves a crater, seeming to having destroyed Zero. As Ziggy reflects on the destruction and subsequent loss of his brother again, his pendant glows, and Zero's body appears, and springs to life, though without any of his memories.
After the credits, Ziggy realizes that Zero's memories are coming back because of the Song of the Unsung. Then the game ends, as they both walk into the distance, proceeding to sing the Song, hoping to bring Zero's memories back.
In Guns N Souls, he lost his life in an incident. Ziggy was framed for the murder of Zero. Which caused Ziggy to be sent to prison. It is revealed that a group called KTK of bunch mechanical soldiers that took his life.
As a trooper
Z.E.R.O is classed as knight classed trooper. Unlike other troopers, he floats over terrain that troopers can’t move to.