Lisa, also known as Risa in Japanese-language materials, is an ARKS operative defined by her intense firearms obsession and volatile personality. This instability manifests as destructive tendencies, indiscriminate targeting of perceived threats, and deriving satisfaction from inflicting suffering with gunfire. Her condition stems from physiological trauma: originally humanoid, severe photonic damage forced an early experimental conversion into a CAST before the procedure was standardized for ARKS.

As a class trainer for Rangers and Gunners in the Central Hall of the Gate Area, Lisa issues client orders. These assignments require trainees to demonstrate proficiency with specific weapons like gunblades, assault rifles, launchers, and twin machine guns, often completing missions with her as the sole partner under challenging conditions.

In combat, Lisa exhibits exceptional marksmanship, uniquely relying solely on visual targeting instead of photons for detection like other operatives. Between Episode 5 and Episode 6, she acquires the Cosmogenic Arm: Hariette the Celestial, enhancing her capabilities.

Her narrative involvement includes critical incidents: she nearly shoots Kohana after mistaking her for Falspawn; assists Ash and Afin during the Falspawn assault on Ship Themis by sniping surrounding enemies; and confronts Ash under Code ABYSS directives, attempting to kill him while expressing enjoyment. Matoi's intervention disrupts the mind control, though Lisa remarks she found the conflict satisfying despite its end.

Following major conflicts, Lisa approaches Ash to cryptically discuss photons and darkness, referencing Photoner philosophy about photons dispelling darkness, though Ash does not comprehend her meaning.