The character known as Holy Sister, whose real name is not provided in the series, serves as the chief inspector of the Adventurers Guild Inspection Bureau and is a prominent figure within the world of Bogus Skill Fruitmaster. She is recognized for holding a position of significant authority, with influence that rivals even that of the guild master, and leads a powerful internal faction known as the Saint Faction. Her primary function is to oversee skill management, maintain records, and enforce discipline, but she often abuses these powers to serve her own agenda, earning her a reputation as a corrupt saint.

In terms of appearance, Holy Sister is a mature woman who dresses in clothing reminiscent of a nun or monastery attire, reflecting her title. She has striking green-blue eyes and is almost always seen wearing a monocle over her left eye, which adds to her stern and authoritative demeanor. Her personality is defined by an extreme and unyielding strictness, with a deep-seated obsession for maintaining order. Above all else, she values powerful battle skills and shows blatant favoritism toward individuals who possess them. She becomes visibly excited by the manifestation of rare combat abilities, such as when Lena Floria receives the Sword Saint skill, but treats those who gain unimpressive skills with cold indifference. Her behavior is consistently arrogant, manipulative, and ruthless, as she refuses to take no for an answer when trying to recruit the talented, forces dangerous assignments on those who oppose her, and takes no responsibility for the problems caused by her personally selected parties.

Holy Sisters core motivation appears to be the accumulation of power, seeking to gather all individuals with strong battle skills to serve the guild and, by extension, herself. She is willing to use any means necessary to achieve this, including coercion, punishment, and secret operations. However, her true goals and the reasons behind her actions remain shrouded in mystery and are never fully explained. Her role in the story is that of the main antagonist, driving much of the conflict that the central characters must face. She is directly responsible for forcibly taking Lena Floria to the holy capital to be trained as a fighter, separating her from her childhood friend Light Underwood. Later, she retaliates against Light for challenging her authority by assigning his newly formed party, Luxeria, to low-paying jobs before sending them on a deadly S-rank quest.

Holy Sister maintains several key relationships. She has a manipulative and adversarial connection with Lena Floria, whom she initially takes under her wing as a prized talent but eventually becomes disliked by for her cruel methods. Her relationship with Light Underwood is more complex; at first, Holy Sister wants to eliminate him because his ability to gain multiple skills is an unexpected and threatening anomaly, but she later decides to capture him alive to exploit his unique power for her own schemes. She is also deeply involved with the character Dratena Belbury, notably being one of the few supporters this hated individual had in the past. Furthermore, she secretly controls a hidden special operations group known as Black Swan, which is composed of individuals with forbidden or powerful skills that leave no official records, and she uses them to carry out mysterious missions behind the scenes.

Regarding her development, Holy Sister does not undergo a redemption arc or a significant change in personality. Instead, her role as a villain solidifies as the story progresses, with her shadowy activities and secret organization being revealed. A notable moment of development occurs when Light Underwood gains a second skill, an event that the anime adaptation depicts as truly shocking to her, causing her to react with disbelief and altering her initial plan to dispose of him. Her notable abilities are largely unknown, which is itself a key plot point. The appraisal skill of the character Ayla Lawrence is incapable of revealing Holy Sisters abilities, as something actively blocks the attempt. This has led to hints and speculation that Holy Sister might possess an appraisal-like skill of her own, or another unique power that prevents others from analyzing her.