The story follows Rushi, a six-year-old girl who retains memories of her past life as a Japanese high school student. After a head injury, she gains the ability to see fragments of the future, including the deaths of those around her. At twelve, she discovers she cannot use magic, while her younger brother possesses all elemental magic, creating a potential conflict for succession in their ducal family, the Ristil Dukedom, known as the sword of the Asteria Kingdom. Foreseeing a future of internal strife and foreign invasion, Rushi resolves to leave home at twelve to allow her brother to inherit and to explore the world. She begins meticulously planning her escape, focusing on securing her safety and financial independence.
Rushi's father, Adolph, a handsome and kind man, takes her to the royal palace to meet Prince Lasmia. Adolph jokingly describes the prince as a "cheeky brat," which worries Rushi. Upon arrival, she is surprised to meet the King, who compliments her resemblance to her grandmother, Ada, a formidable warrior. Prince Lasmia, upon meeting Rushi, expresses disappointment that his future sword is female, displaying a blatant disregard for her. Rushi, unimpressed by his rudeness and sexism, politely but firmly rebuffs him, leaving the prince stunned and her father amused.
Rushi begins training in swordsmanship under Klaus, a stern but kind former subordinate of her grandfather. She recognizes the need for combat skills for her future independence. Her grandmother, Ada, a legendary strategist known as the "Ogre Princess," visits and expresses concern that Rushi is "too adult" for her age, sensing a change in her since a childhood accident. Meanwhile, Rushi's mother announces her pregnancy, and Rushi, despite her foreknowledge of a potential succession crisis, feigns happiness. She touches her mother's belly and feels a kick, reinforcing her belief that it will be a boy. The birth of her brother, Glenn, is marked by an unusually powerful cry that Rushi perceives as magical. She witnesses her father and grandfather collapsing in exhaustion after the birth, and her grandmother announces the healthy birth of a boy. Rushi touches Glenn and sees four colors of magic surrounding him, confirming his prodigious talent. Her father, Adolph, witnesses Rushi's finger heal instantly after an injury, recognizing it as "divine power" and making her promise to keep it a secret, increasing his concern for her safety.
Six months later, a young, emotionless boy named Luca is introduced as Rushi's attendant. Luca, who was found and raised by Adolph, has been trained since Rushi's birth to be her protector. He is exceptionally skilled and anticipates Rushi's needs, though his lack of expression makes him difficult to read. Rushi learns that Luca was once an assassin sent to kill Glenn but was instead tasked with protecting the Ristil family. He harbors a deep loyalty to Rushi, having been moved by her infant innocence.
Rushi's plans for escape are further complicated by the arrival of Prince Lasmia, who seeks to apologize for his previous rudeness. He expresses his desire for Rushi to be his future sword, despite his initial disappointment at her gender. The King, observing Lasmia, notes that he has a "lost item" aura around Rushi, suggesting she will eventually disappear from his life.
Later, Rushi attempts to leave home again, but her father finds her at the gate. He comforts her and, upon seeing her finger heal instantly, reiterates the need for secrecy regarding her "divine power," increasing her security. Rushi, though initially disheartened by her failed escape attempt, begins to accept her situation.
The narrative then shifts to an external perspective, revealing that numerous assassination attempts have been made on the Ristil family. A powerful figure, likely a high-ranking official or even the King, is shown to be aware of these attempts and has taken measures to counter them, even eliminating those who have betrayed the kingdom.
Rushi continues to plan her escape, now with the added complication of her younger brother, Glenn, who possesses all four elemental magic types and is destined to be a genius. She realizes her foreknowledge of a succession crisis is likely to come true. Her escape plans are further hindered by the constant presence of Luca, her exceptionally capable attendant, and the increased security around the family due to the threats they face. Rushi also learns about the Ristil family's matriarchal history, where women held significant power, a stark contrast to other nations.
Prince Lasmia visits Rushi again, this time to apologize for his past behavior. He expresses his willingness to accept her as his future sword, regardless of her gender. Rushi, though initially surprised by his sincerity, finds him less disagreeable. She also learns that Glenn, her brother, seems to calm down when she is around.
The story concludes with Rushi contemplating her escape, realizing that her foreknowledge of a succession crisis is becoming a reality with Glenn's birth and prodigious magical talent. Despite her affection for her family, she feels a growing sense of displacement and resolves to leave. Her escape plans are still in their early stages, facing significant obstacles like border controls and the need for identification. Meanwhile, Luca, her devoted attendant, is revealed to have been trained since Rushi's birth to protect her, having been an assassin who was spared and tasked with her safety. He harbors a deep, unspoken affection for Rushi, stemming from their first encounter as an infant.
