HP: The Arcane Thief - Chapter 12: The encounter with the Mafia Prodigy

Xin Yun, a sarcastic young man, traveled to an unknown world by chance, but lost his chance to become the strongest because of his obsession with women... or sex. In a collision of the powers of nine powerful men, an incredible thing happened. Xin Yun was reborn back to the time when he traveled to the Isekai world. A fantasy journey is about to begin... [The comic adapted from this novel is popular all over the world]

The more he got to the Comprehensive world, Beiyuan Baiqiu originally thought it was just an ordinary Comprehensive daily world.

Who would have thought that after entering high school, unusual things would happen one after another, and I would awaken myself through the simulator.

Since then, Beiyuan Baiqiu has embarked on the road of being invincible.

[Demon Slayer, Campione!, No Game No Life, Problem Children are Coming from Another World…]

- Description from novelbuddy

Kubei was just an ordinary pencil and button pusher working a day job, hating his boss and making horrible speeches when one day he fell asleep after pushing an all-nighter. When he woke up, he was bound to a chair, facing three creepy robed women and in a body way too young and way too weak to be his own. As he slowly came to, he realized that he was no longer in the same universe as he was before. He had teleported to the Kingdom of Helius, where an all-powerful church rules its lands and wages war against the elusive group known only as Mages. Armed with an incredibly cocky neural interface that just won’t shut up and his own sheer wit, our MC will find himself not just fighting to survive, but maybe even something bigger than himself.

One day, when a novelist woke up from a restless sleep,he realized that he had transformed into his 12-year-old self.