Lady Serena, a noblewoman known for her wicked schemes, is betrayed by the crown prince to whom she was engaged. Framed for a murder she did not commit, she is executed by poison. However, instead of dying, Serena awakens in the past at the moment of her birth, retaining all her memories from her previous life. Reflecting on her downfall, she concludes that her failure was not due to flawed plotting but a simple lack of competent underlings to carry out her orders.

Determined to rewrite her fate and exact revenge, Serena decides to forge her own elite force from scratch. She visits a destitute orphanage and recruits a group of desperate children, putting them through a brutal and ruthless training regimen. This process transforms the orphans into the Twelve Eyes, a group of six fiercely loyal and lethally skilled operatives who serve as her personal assassins and bodyguards. The title refers to Serena and her six squires, each possessing two eyes, making a total of twelve that watch her back and execute her will.

The story is set in a fantasy kingdom with a rigid noble society. The central conflict pits Serena and her growing faction against the crown prince, the saintess, and the established powers that orchestrated her execution in the original timeline. Serena does not seek redemption; her goal is to use her knowledge of the future, her sharp wit, and her fanatically devoted team to dismantle her enemies and seize the life she believes she deserves.

Several notable narrative arcs structure the plot. The first arc follows Serena's childhood as she secretly locates and recruits the orphans who will become her Twelve Eyes. A significant portion of the story focuses on the training phase, showcasing the harsh methods Serena uses to mold the children into ruthless killers, creating a dynamic that is both dark and darkly comedic. As the orphans grow into a formidable squad, Serena begins to execute her revenge, leading to a series of confrontations where her morally flexible tactics clash with the kingdom's conventional nobility. The narrative takes a dramatic turn approximately eighty percent through the story, shifting from a calculated revenge plot into unexpected territory with significant emotional stakes. The light novel concludes with a clearly defined ending, followed by an after-credits scene that recontextualizes much of the preceding events, leaving the story self-contained rather than setting up an ongoing serial.