The protagonist, a legendary and ancient Onmyoji known for his immense power and feared for his mastery of forbidden arts, finds himself on the brink of death within his burning mansion. Betrayed and outmaneuvered by a conspiracy orchestrated by unknown nobles or royalty, he has lost his disciples, turned against the imperial court, and was even forced to fight a beloved child. His left arm is gone, his lungs are seared, and his once formidable arsenal of talismans, Shikigami, and even a powerful Oni are defeated. Realizing that raw power was insufficient, he acknowledges his fatal flaw: a lack of cunning.
With his dying breath, he performs a forbidden reincarnation ritual using a final talisman, vowing to be more cunning in his next life and achieve happiness. He awakens as a toddler, Seika Lamplogue, in a dimly lit room, a hexagonal magic circle with strange stones at its vertices drawn around him. A ritual is underway, led by a man and two older boys, presumably his family. The ritual fails to awaken any magical aptitude in Seika, much to the disappointment and mockery of his father and elder brothers, Glay and Luft. Seika, however, feels an immense surge of spiritual power within him, contradicting their assessment of him being "magicless."
Ten days later, Seika, now three years old, confirms he has been reincarnated into a different world. Observing two moons and unfamiliar constellations, he deduces this is an isekai. He learns his name is Seika Lamplogue, and he belongs to a noble family, the Lamplogues, who are renowned for their magical research. Despite being the third son, he considers this fortunate, as his previous life began in poverty and ended in an early death. He also notes the world appears more advanced than his former Japan, possibly rivaling or surpassing ancient civilizations like Rome or the Islamic Caliphates.
Four years pass, and Seika is now seven. He secretly practices his Onmyoji arts, creating paper Shikigami from leaves and using them for reconnaissance. He learns that his new world is part of the powerful Urd Wight Empire, a peaceful and prosperous nation with a unique four-element magic system (fire, water, wind, earth), supplemented by light and darkness. Threats exist in the form of monsters and demons. Seika also dedicates himself to making paper, a valuable commodity, to create more sophisticated Shikigami. He discovers that his fallen baby teeth can also be used as magical tools.
Another four years later, Seika is eleven. He has been diligently studying and preparing. He witnesses his older brothers, Luft and Glay, practicing magic. Luft demonstrates proficiency with wind magic, while Glay, despite his arrogance, struggles with fire magic. Seika, feigning a lack of magic, is offered Glay's staff and, to everyone's astonishment, unleashes a powerful, blue-flamed fire attack that obliterates the target. His father, Blaze Lamplogue, the head of the family and a respected magic researcher, is intrigued but dismisses it as an anomaly, assigning Seika a tutor instead of allowing him to formally study magic.
Seika also encounters Eefa, a slave girl who possesses the ability to see spirits and other unseen entities. He discovers that Eefa's unique sight is connected to spirits that are drawn to magic. He uses his knowledge of summoning to create "hitogata" (humanoid paper figures) to summon "hitodama" (will-o'-the-wisps), which Eefa, with Seika's guidance, learns to control. This marks a significant step in Seika's plan to gather allies and further his goals in this new world. He also learns that Eefa desires freedom and to explore the world, a sentiment he shares. He begins to subtly manipulate events, using Eefa as an informant and a means to conceal his own activities. He also realizes that his own presence seems to strangely affect the spirits, making them act erratically.
Finally, Seika, now eleven, has spent years preparing. He has honed his skills, gathered information, and made a crucial ally in Eefa. He has also witnessed Glay's continued bullying, now directed towards Eefa, and intervened. Seika's ultimate goal remains shrouded in mystery, but his actions suggest a long-term plan involving the manipulation of magic, spirits, and potentially the political landscape of the Urd Wight Empire.
