Shin, a boy with memories of his past life, was taken in by an old man known worldwide as "the Sage," a master of all magic who had saved humanity from countless calamities.

Raised as the Sage's grandson away from the mundane world, Shin utilized his past life memories to thoroughly absorb all of the Sage's techniques, growing to the point where he could even develop magic himself.

Then, upon turning 15, just as he was about to become independent, his grandfather said:

"Oh, I forgot to teach you common sense."

To teach his grandson, who had grown up utterly lacking common sense, about the ways of the world, the norms of society, and how to interact with people, he enrolls him in the "Earlshide Advanced Magic Academy" located in the Royal Capital of the Earlshide Kingdom.