Fia Note serves as an agent dispatched from the magical lunar city of Sosarium. Operating under the code name Angel Rabbie and the human identity Lasty Farson, her primary function involves intervention at critical historical junctures to prevent humanity from repeating past conflicts, specifically the catastrophic "Big Magic War." This devastating conflict, fueled by the misuse of combined science and magic, left Earth plagued by dangerous remnants like genetically engineered creatures and destabilizing technologies that threaten the fragile rebuilding efforts of surviving populations.

As Lasty Farson, she exhibits notable clumsiness and inefficiency in daily activities, including tardiness on her first official assignment day. However, this human persona undergoes a significant transformation upon assuming her angel role. Becoming Angel Rabbie grants her considerable combat capabilities and effectiveness, creating a sharp contrast with her otherwise hapless demeanor.

Her debut mission commenced with deployment to Earth shortly after her delayed arrival for duty. Tasked with aiding a village community, she confronted a group led by a woman stealing essential food supplies and resources from the local population. During this operation, she successfully neutralized the threat posed by reactivated combat robots originating from the earlier war era, demonstrating her capability despite her rookie status.

Concurrently with her primary mission, Fia Note pursued investigative leads regarding the prolonged disappearance of her fellow angel operative, Lukia Shawl. Presumed deceased by Sosarium authorities due to her extended absence, evidence gathered during Fia Note's mission indicated Shawl's unexpected survival and suggested her potential involvement in unauthorized or independent activities separate from the angel mandate.