Fia Ruud, born into a knightly lineage, initially ranked as her siblings' least skilled swordsman. A near-fatal dragon encounter violently resurrected memories of her past life as the "Great Saint," who aided her brother in defeating the Demon King. That existence ended in betrayal when her brother abandoned her post-victory, leading to torture and execution by the Demon King's lieutenant. This entity explicitly vowed to kill her upon any reincarnation as a saint, forging her profound terror of discovery.

Now, alongside these traumatic memories, her latent saintly powers reawakened: potent healing, protective magic, and combat strength. Despite their potential, she actively suppresses them, haunted by fear of persecution and reliving past agony. This internal battle defines her; innate compassion constantly wars with self-preservation, compelling her to secretly use her abilities to help others, even as she outwardly dedicates herself to earning knighthood through rigorous conventional training.

Her path demands navigating complex relationships while guarding her perilous secret. She forms a deep bond with the black dragon Zavilia, her familiar. Their connection is one of mutual sanctuary: he protects her, and she shelters him, often disguising his formidable presence. She interacts extensively with knight brigade leaders like Cyril Sutherland and Saviz Náv. Cyril exploits her perceived resemblance to the Great Saint to heal historical rifts in his territory, unaware she *is* that reincarnation. This forces her to meticulously balance alleviating suffering with preserving her façade.

Her development sees her rise from trainee to full knight. Post-graduation, missions take her across regions like Sutherland and Blackpeak Mountain. These assignments involve confronting epidemics such as yellow-speckle fever and reconciling deep-seated conflicts between communities and knights. These experiences gradually challenge her isolation, as figures like Kurtis – a knight regaining memories of serving her past self – deduce her true identity and pledge renewed allegiance. Her actions, however, inadvertently draw scrutiny, especially during public events like miraculous interventions in performances or strategic contests with royalty, constantly risking exposure.

A resurgence of demonic threats further strains her concealment. Encounters with demonic entities, including a black-haired demon girl, evoke past-life traumas and provoke questions about demonic nature and infiltration into human society. These incidents test her resolve to remain hidden, as her suppressed powers become increasingly vital to counter the emerging dangers.

Throughout, Fia's arc intertwines the tension between self-preservation and altruism, the crushing burden of her dual identity, and the incremental erosion of her secrecy through both voluntary heroism and external pressures. Her relationships – with dragons, knights, and royalty – continually shape her choices, compelling her to navigate a precarious existence where every act of kindness risks unraveling her hard-won anonymity.