One of the Irregular Hunters, B-Rank. Friends with Zero, Axl, and Guest. He has a kind heart and is energetic, but is quite quiet around people he meets for the first time. His weapon is the X-Buster (a weapon that instantly retracts his hand into his forearm to reveal a muzzle, firing bullets of condensed solar energy).

One of the three Irregular Hunters, S-Rank. A robot with a cool, stiff, and cold-headed personality. Friends with X, Axl, and Guest. His weapon is the Z-Saber (a laser sword).

One of the three Irregular Hunters, B-Rank. Friend of X, Zero, and Guest. He is energetic and cheeky, acting as the mood maker. His weapon is the Axl Bullets (dual pistols).

A villainous character with an evil personality. He is the king of the Irregulars and controls them. He is currently spreading a hacking chip.

Due to a malfunction in his electronic brain, he disregards means and consequences to destroy Irregulars. Rather than eliminating hazards, he seems to enjoy the 'hunt.' He is a being only a paper-thin margin away from being an Irregular himself. Because of this, he was removed from duty and detained. He has a cold and eccentric personality.

A gentle and kind assistant to the Irregular Hunters. She is a supporter and does not participate in combat. She tends to use polite speech. She and Zero like each other, but neither of them knows it.

An operator and navigator belonging to the Irregular Hunter Headquarters. She is in a relationship with Gate, though they bicker. She has a kind and affectionate personality.

A researcher for the Irregular Hunters who serves as the head of the laboratory. He is dating Alia, but they occasionally bicker. He has an arrogant and cynical personality.

The Commander-in-Chief of the Irregular Hunters. While his personality is cool-headed and calm, he has a strong sense of care for his fellow Reploids.