A failed assassin, known only by her code number 9956, loses her life during a mission to eliminate a prince. Instead of vanishing into nothing, she awakens as Selena Violette, the infant daughter of a powerful duke in a world of magic and nobility. Retaining all the memories and lethal skills of her past life, she believes assuming the role of a pampered noble will be effortless. She quickly finds that high society presents a different kind of battlefield.

Selena’s new family is her first challenge. Her biological mother is a naive airhead who becomes frightened of her daughter's unnerving demeanor. Her stepsister, a commoner adopted into the family, is a scheming manipulator who uses tears and deceit to turn everyone against Selena and secure her own position. Instead of the subtle political games she expected, Selena finds herself dodging petty harassment and enduring tea parties filled with shallow rivalries, all while suppressing her instinct to resort to lethal force. Her cold, logical personality and inability to feign warmth lead to her being ostracized, leaving her isolated despite her high status.

The central conflict ignites when Selena discovers her stepsister has become engaged to the second prince. Seeing this as a final provocation, she decides to flee her family home. Her escape is interrupted when she literally bumps into the first prince, Evan. Far from being offended, Evan is fascinated by the duke’s daughter who acts nothing like a typical noble. His investigation into her reveals nothing but contradictions, and he becomes determined to unravel the mystery of the cold, competent, and lethally capable Selena.

Throughout the first volume, Selena navigates the treacherous waters of an academy filled with ulterior motives. She uses her assassin’s skills to dismantle social traps and counters harassment with an icy glare and fierce verbal ripostes. A major turning point occurs during a hunting party, where a noble she had humiliated unleashes a monster on the guests. For the first time, Selena is forced to fight not just for her own survival, but to protect the other nobles, including her tormentors. This event solidifies Prince Evan’s interest and begins to crack the stone-cold heart of the former assassin who has never known love.

The second volume shifts focus as Selena is tasked with overseeing three international exchange students from a neighboring kingdom. The group includes Shaghad, the melancholic and legitimate son of a crown prince, and his two half-siblings, Ismail and Aisha, who are the children of their father’s mistress. It quickly becomes clear that Aisha aims to seduce Prince Evan, while Ismail plans to eliminate Shaghad to secure the succession. Selena, acting as a protector, is forced to use her assassin’s expertise for a new purpose: saving lives rather than taking them. She trains the despondent Shaghad to defend himself and dismantles the assassination plots, all while wrestling with the irony of someone killed by a knight in her past life now serving as a prince’s guard.