I have an Apocalypse City - Chapter 201 - : Pet Contract

Magic. It is a product of neither legends nor fairy tales, but instead has become a technology of reality since a time unknown to people. Supernatural power became a technology systematized through magic, while magic became a technical skill. A “Supernatural Power User” became a “Magic Technician”. Magic Technicians (in short, Magicians) are nurtured through Magic High Schools and Universities. This is a story about: A defective elder brother and low achiever. A perfect, flawless younger sister and high achiever. After both siblings entered a Magic High School, The stage of daily turbulence was unveiled —.

[Character Deleted.]I deleted the character I had been raising for over 5 years.To finally defeat the final boss of Demon Fantasy—the one I could never quite beat.For the sake of defeating ‘Baal’.“…I can just start over. I can do it.”And then…[Special reward has been granted!]“What? A mythic-tier trait?”The perfect opportunity had arrived.“This time, for sure!”I’ll raise the strongest mage and take down Baal!At least, that’s what I thought when—[Welcome to Demon Fantasy.]I found myself inside a world teeming with 666 kinds of demons.And I had the ‘special reward’ I just received!“…Fine. Let’s see who wins this.”I was confident.After all, I’ve been a veteran of this game for 10 years.

A story about a traveler who crossed into a parallel universe, relying on his Proficiency ability to continuously grind experience and become stronger.