A brilliant middle-aged scientist, Sagami Shirabe, dies and is reincarnated in a fantasy world as Grey Millard, the eight-year-old third son of a destitute noble family. His new body grants him cheat abilities: Magic Design, Circle Domain, Universal Item, and Universal Teleport. However, his circumstances are dire. His father is under the thumb of a cruel stepmother who mismanages the territory, leaving the family on the verge of ruin. Grey is also subjected to harsh treatment and, at age thirteen, is forcibly exiled from the Millard territory.

Rather than despair, Grey embraces this freedom. Combining his sharp adult intellect with his supernatural skills, he sets out to explore the world and carve his own path. His journey takes him through dangerous lands, where he uses his powers and knowledge to overcome obstacles, gain allies, and steadily rise in power and influence. Notable arcs include his early struggle for survival after exile, the formation of bonds with characters such as Satella—a girl whose parents were killed by monsters—and his gradual transformation from a cast-off noble into a force that challenges the established order. The story follows his adventures as he leverages his past life’s expertise and his unique abilities to rewrite his destiny in an unfamiliar realm.