At age three, Tafelina Lowell Lera Duval experienced a dramatic mana fluctuation that changed her hair and eye color, leading her noble birth parents to disown her and send her away. This apparent tragedy became a blessing in disguise. She was taken in by the kind Earl of Peylon and raised in a remote, monster-filled region of the fantasy world Ozeria. There, her extraordinary magical talents flourished. She also discovered she possessed memories of a previous life in Japan, which she used to invent various magic tools and live a comfortable, if unconventional, life hunting monsters in the forest.

The protagonist, who goes by Lera, is a reincarnated individual whose overpowered magic and inventive genius make her a prodigy far beyond her years. Her personality is generally laid-back and unflappable, and she is known for her ability to remain cheerful and "not disheartened" no matter the situation, a trait some critics find leaves her with little room for emotional growth. Her peaceful existence is disrupted as her thirteenth birthday approaches. Because she is technically a noble's child, she is forced to leave her beloved home in the countryside to attend a special academy in the royal capital, designed to educate the next generation of nobility. This move throws her into a world of political intrigue, social maneuvering, and unexpected trouble.

The main narrative arc of the first volume follows Lera as she navigates academy life in the sprawling capital, where she feels like a fish out of water. She quickly becomes entangled in a series of events, including a kidnapping attempt and the sudden appearance of her hostile half-sister, Ribbons, who had been brought in to replace her in the family. Despite these conflicts, which set up a long-term rivalry with her birth family, Lera’s overwhelming power and the loyal friends she makes allow her to overcome most obstacles with ease.

In the second volume, Lera returns home to the Peylon earldom for summer break, hoping to relax and enjoy the annual hunting festival in the Mystic Forest. Her vacation is far from quiet, however, as she receives an unexpected marriage proposal almost immediately upon her return. The volume focuses on her dealing with these new social responsibilities, the appearance of overdressed and unwanted visitors, and the mysterious movements of royal knights in her beloved forest, all while trying to enjoy time with her old friends. The third volume sees Lera return to the royal capital for a new school year. Her hopes for a peaceful term are dashed when an older student begins harassing her, dragging her into a larger dispute. The situation is further complicated by a surprise visit from her estranged birth father and the continued antics of her rival, Ribbons. On a brighter note, she finally acquires a formidable new mount—a man-eating bear that is not afraid of her immense magical power. A notable element of the series is the gradual development of magical technology; Lera uses her past-life knowledge to invent things like magic screens, teleportation portals, and dimensional storage bags, essentially recreating modern conveniences like smartphones in a fantasy setting.