sage grandson

Edel, a boy who fell into the demon world when he was a baby, was lucky enough to be picked up by an old man and raised.
However, when he was twelve years old, his grandfather who raised him died.
Following his grandfather's will, he went to an acquaintance of his grandfather who was in the human world.
That acquaintance was the hero Maribel, who was praised as one of the Four Heroes.
After that, Edel decided to attend the hero school due to Maribel's arrangement.
But he didn't know.
He remembers that the demon world where he was born and raised was a tremendously hard environment compared to the human world.
That his grandfather, who raised him, was a legendary great sage who was adored by the Four Heroes as "Sensei". His grandfather gave him a Spartan
education in the harsh demon world, and he himself has acquired powers that are beyond common sense .