Leia Westoria serves as the saint of the Kingdom of Elshaid, using her magical abilities to create barriers that protect the realm from monster incursions. Her life unravels when her younger sister Jill, who possesses no saintly powers, accuses Leia of abuse and mistreatment. Jill casts herself as a tragic heroine suffering at the hands of a cruel sibling, a performance convincing enough that Leias own fiancé, a duke, breaks off their engagement and promptly becomes engaged to Jill instead.

While Leia is performing her saintly duties reinforcing barriers in a forest, she is confronted by Crown Prince Eric, a man renowned for his rigid and uncompromising sense of justice. He has heard Jill's accusations and arrives prepared to condemn Leia. Instead of accepting this fate, Leia finally snaps and defiantly demands that the prince actually investigate the situation rather than believing the rumors. Taken aback by her response, Eric does precisely that and discovers the truth. He apologizes and makes an unusual offer: he wants Leia to live in the royal palace and serve as one of his personal bodyguards, a position that will allow him to observe her character directly while also protecting him from the numerous assassins who target him regularly.

Leia accepts the position and is thrust into a world of royal politics, conspiracies, and constant danger. Her saintly abilities prove unexpectedly useful in neutralizing threats before they reach the prince, and her strong sense of duty and competence gradually earn Eric's trust. The narrative frequently shifts perspectives, revealing the inner thoughts of other characters. Prince Erics point of view shows a man under immense strain, whose relentless pursuit of justice has left him isolated and with many enemies. More notably, the story periodically enters the mind of Jill, Leias younger sister. These segments expose the full extent of her delusions of grandeur and her self-centered worldview, where she genuinely believes herself to be the victim of a cruel narrative and remains oblivious to the damage she causes. Her main character syndrome makes her an unwitting pawn for others to manipulate.

As the story progresses, the conspiracy against Prince Eric deepens. The investigations reveal that Duke Berklein, a powerful noble who wants the prince dead, is entangled with Jill, who has begun cheating on her former fiancé with the duke. Further inquiry shows that Jill is experimenting with Death Poison, a dangerous substance that elevates the stakes of her foolish schemes to a lethal level. The first major arc concludes with the exposure of the corrupt parties and Jills role in their plots, though she is not executed but instead confined. The series continues with Leia and Eric announcing their engagement, only to face opposition from the nobility who resent having their power stripped away. A diplomatic envoy from the Ren Empire arrives, bringing Lingshas brother Liu, who breaks into the palace and makes a shocking proposal. The empires real goal is to convince Eric to marry Lingsha instead of Leia, or alternatively to have Leia return to the empire with Liu.