The story begins with Nakamine Touji, a middle schooler, habitually visiting the rooftop of his cram school late at night to gaze at the moon. One night, he witnesses the moon seemingly waver, only to realize the rooftop itself is unstable due to the building's age and modifications. A massive earthquake strikes, and Touji falls from the collapsing rooftop.
He awakens in a void, a space between worlds, where he encounters his deceased friend, Yuu Akashi. Yuu reveals that Touji died in the earthquake and that he is now a god scout. Yuu explains that Touji's soul and spirit are intact and can be reincarnated into another world, a condition of Yuu's own ascension to godhood. Touji eagerly accepts, requesting a fantasy world with cheat-like abilities. Yuu agrees, with the condition that Touji assist the heavens when needed, and sends Touji's soul to "World Number 23079" for reincarnation.
Touji is reborn as Alysia Mel Latromia, a baby girl in a world where vampires are a recognized, long-lived race. Her parents, Nadia and Orlas Latromia, are powerful vampire nobles known for their advocacy of interspecies equality. Alysia, retaining Touji's memories and intellect, quickly masters the local language and exhibits an astonishing aptitude for learning, far surpassing typical infant development. She also possesses a unique ability to manipulate paradoxes, a power granted by a Valkyrie who communicates with her, and latent magical potential including minor spiritual, demonic, and divine energy.
By the age of eight, Alysia has devoured vast amounts of magical knowledge, though her mother forbids her from practicing until she is eight. Upon receiving permission, her first attempt at a simple fire magic spell results in an uncontrolled explosion that scorches fifty meters of forest, revealing the immense power of her magic and her overwhelming mana reserves. This leads to rigorous training in a specially prepared underground chamber to control her magic.
Three years later, at eleven, Alysia has mastered intermediate magic and is researching flight magic, a concept absent in this world. She successfully develops her own original flight spell, a significant achievement.
On her twelfth birthday, Alysia is invited to the Royal National Magic Academy by the King, who had previously proposed marriage to her for his son, an offer Alysia vehemently rejected, much to the King's bewilderment. Alysia's parents, concerned about her unusual lack of vampiric bloodlust and her immense power, prepare her for the academy.
The day before her departure, Alysia is attacked in her home by a swordsman wielding lightning magic, who claims to be acting on the King's orders. He fatally wounds Alysia by stabbing her through the heart. In her dying moments, Alysia calls upon the gods to grant her immortality, a request that is granted. She awakens, healed and immortal, and proceeds to break the hypnosis spell that incapacitated her household, including her parents.
Upon returning to her family, Alysia, now possessing the ability to use magic without the need for the magic circle, demonstrates her power by conjuring a powerful darkness wall. She then uses a detection spell to locate her family and the attacker in the kitchen. A fierce battle ensues, during which Alysia realizes the attacker is not acting directly on the King's orders but is motivated by her rejection of the King's proposal. Despite her efforts to avoid collateral damage and protect her sleeping family, Alysia is ultimately struck down again. However, her newfound immortality allows her to survive. She then breaks the hypnosis spell on her family and prepares to depart for the magic academy, still wary of potential threats.