The story takes place in the Kingdom of Zied, a fantasy realm where a temple dedicated to the Goddess of Healing raises candidates to become the realm’s Saintess. The protagonist, Rua Restoat, is a 17-year-old orphaned baron’s daughter who possesses a unique and devastating healing ability: she can only cure others by physically transferring their wounds, illnesses, and pain onto her own body. Because of this flaw, she is ridiculed by the temple’s other inhabitants and is infamously known as the Broken Saintess. Her only solace comes from her best friend, Arianne, who appears to defend her from constant mockery.

Rua holds affection for Garrett Vance, a captain of the Royal Knights. When Garrett is mortally wounded in a fight against a demonic beast, Rua uses her powers to save his life, but collapses from the sheer agony of his injuries. When she finally awakens, she is shattered to discover that Arianne has taken full credit for the miracle healing. To make the betrayal worse, Arianne is now engaged to Garrett and is set to be named the new Saintess, a position left vacant for the past decade. The temple and the people continue to deride Rua as broken and worthless. In her despair, she begins to turn her power inward, discovering she can inflict the pain she has absorbed onto others. She takes bitter satisfaction in making her tormentors suffer as she has.

Her descent into vengefulness catches the attention of Sven, the second prince of Zied. Despite his reputation for being cursed, Sven is observant and kind. He reveals a deep conspiracy: the Temple’s High Priest plans to unleash an artificial, incurable disease upon the kingdom. His scheme is to have his sponsored Saintess, Arianne, heal the infected, thereby garnering immense public support for the Temple and allowing him to seize control of the throne. After witnessing a clandestine meeting between the High Priest and Arianne, confirming Sven's accusations, Rua agrees to join his cause. She decides to use her cursed powers not for healing, but as a weapon for revenge against those who wronged her.

The narrative focuses on Rua’s transformation from a kind-hearted healer into a calculating anti-heroine. She learns to weaponize her pain-absorbing ability, using it to poison enemies and fight back. As she allies with Prince Sven, they work to expose the corruption within the temple while navigating political intrigue. Arianne is revealed to be deeply manipulative and sadistic, having orchestrated Rua’s isolation for her own amusement. As Rua gains public support through her actions, Arianne grows increasingly jealous and unhinged, leading to a final confrontation where Rua reclaims her agency and clears her name. The story also explores the growing bond between Rua and Sven, a kindred spirit who has secretly loved her since she healed him in his childhood, culminating in her recognition as the true Saintess by the will of the people.