Diana, originally named Sanya, is a central figure in the anime. Her background begins in a humble village, where she lived as an ordinary girl until a pivotal moment in her childhood. After falling asleep listening to a story about the legendary Saint Diana, she awoke to discover she had been granted a miraculous blessing, bestowing upon her the powers of a saint. This divine selection led to her immediate recruitment by the Dianist Clergy, who removed her from her family and home. Adopting the name of her predecessor, she became the public-facing symbol of the Dianist faith, a role she has struggled to reconcile with her memories as the simple village girl Sanya.

Diana’s personality is defined by a deep and persistent insecurity. Beneath her public persona as the cutesy and gentle saint lies a person riddled with self-doubt. She feels profoundly unworthy of her title, believing she did nothing to earn her extraordinary powers and that her abilities cannot compare to those around her. A key source of this anxiety is her relationship with Scarlet, towards whom she harbors a mixture of deep admiration, jealousy, and a fragile sense of purpose. These feelings of inferiority and her fear of being useless leave her emotionally vulnerable and susceptible to outside manipulation.

Diana’s primary motivation stems from a desperate need to be valuable and to avoid being abandoned. Her worst fears are realized when she loses her saintly powers, an event that leads the Dianist clergy, who had previously revered her, to quickly deem her useless and cast her aside. It is at this point of feeling utterly worthless that Dios approaches her with a proposition. Desperate to restore her powers and regain a sense of purpose, Diana agrees to a betrayal: she provides information to the rival Palmian faction in exchange for their promise to restore her blessing. While she accepts this deal, she tries to impose the condition that her friends not be harmed, revealing that her actions stem from desperation rather than malice.

In the story’s present, Diana fulfills the role of the traitor among the Dianists, whose guilt-ridden actions significantly raise the stakes. Her role is also that of an emotional anchor for the protagonist, Scarlet. While Scarlet is the physically invincible heroine who resolves conflicts with her fists, Diana represents the more fragile, human side of their partnership, often serving as a damsel in distress who requires protection. Despite her betrayal, she remains a sympathetic figure, constantly wracked with guilt over her choices, particularly as she watches over the unconscious Scarlet, whose condition she feels responsible for.

Her key relationships are central to her character arc. Her bond with Scarlet is the most significant; Scarlet acts as a protective and confident older sister figure, the very ideal Diana feels she cannot live up to. She develops a crush on Leonardo, Scarlet’s brother, which reveals a more vulnerable and romantic side to her. The most pivotal relationship is with Dios, who is revealed to be her secret half-brother. Though he is an agent of the enemy, his actions are driven by a twisted, obsessive love for his sister, as he believes working with Palmia is the only way to restore her smile and powers.

Diana undergoes significant development, transforming from a seemingly one-note comedic foil to a deeply flawed and complex individual. The discovery of her betrayal is a major turning point in the narrative, forcing her to confront the weight of her choices and the consequences of her jealousy and envy. Her arc forces her to move from a position of passive insecurity to actively facing her failures and seeking atonement. In a moment of crisis, she attempts to protect the still-unconscious Scarlet from Dios, an act of bravery that helps to redeem her in the eyes of both the characters and the audience, demonstrating her fundamental goodness despite her severe lapse in judgment.

Regarding notable abilities, Diana originally possesses the miraculous powers of a saint, bestowed upon her by a goddess. These powers are what define her public identity and value within the Dianist church. However, at a certain point in the story, she loses these abilities, which triggers her subsequent feelings of worthlessness and her decision to betray her allies. In her powerless state, she is portrayed as a non-combatant who must rely on others, particularly Scarlet, for protection.