Since he was surrounded by normal people, Itsuki was filled with confidence when he found out he was special during elementary school
But when he finally went to the special school, he found out that his power was nothing. He ran to games to console himself.
In most Manga and Light Novels, the main character has some sort of superior ability.
However, in an actual society based on special powers, there are people all over the spectrum. It may be hell for the lower people.
Within his culture of ESPers, he saw numerous people perform amazing feats, and defeating evil. He wished to be like that.