Zero, the deuteragonist, is a lachter capable of materializing objects through her ability, Lacht, though her powers remain more limited than those of others. Her past is marked by a traumatic childhood as a test subject in Barton’s research facility, where he sought to cultivate and steal lachters’ abilities. Designated “Unit Zero” during this period—a name she later reclaims—she is freed when Inyo defeats Barton, sparking her unwavering loyalty. She becomes his devoted assistant and housemate, anchoring her identity to his cause.

A teenage girl with waist-length blonde hair, blue-green eyes, and a petite frame, Zero wears a light pink dress with pinkish-brown sleeves, paired with a dark blue headset adorned with silver cat-ear ornaments and the numerals “04.” Her demeanor blends gentle kindness with fierce protectiveness toward Inyo, whom she formally addresses as “sir,” managing his daily needs with quiet dedication. This caretaker role contrasts with fleeting insecurities about her appearance and a playful obsession with pudding.

Her Lacht enables her to craft tools like drones, controllers, and surveillance screens, provided she understands their mechanics. These creations prove vital during missions, particularly her drone, which navigates hazards to safeguard Inyo. While instrumental in their operations, her narrative significance deepens when her history resurfaces: Barton’s recapture of her forces Inyo to confront his limitations, exposing their mutual reliance.

Zero’s development oscillates between lighthearted moments—comedic attempts to impress Inyo or navigate clashes with clients—and darker arcs where her trauma tests their bond. Her journey traces a path from victimized test subject to resilient partner, her loyalty and growth framing her as both a survivor and proactive ally against Magmell’s threats.