Toaru Majutsu no Index - Volume 3, Chapter 3: Railgun. Level5.

Fanatic virtual gamers:
Tired of the stereotyped linear drama emotions? Want to try a real open world game?
Are you tired of playing an RPG that can only play a role? Want to lead the subordinates in virtual reality and experience the thrill of governing the army?
Welcome to the massive open killing game “War in Heaven”.
……
Seeing the game’s winning and losing judgment mechanism, a professional player who is interested in PVP for 20 years and is also very interested in AI, has a bright smile:
“It’s time to show the real killing method… How about building an AI army by the way?”

- Description from Uukanshu translation

In the final year of high school, Christian’s ordinary life takes a dramatic turn when he is struck by lightning, awakening the Idle System, a manifestation of his dream.What begins as a personal fantasy quickly transforms into a new reality for Christian, who revels in his newfound abilities while the world around him remains blissfully unaware.However, as Christian adjusts to his extraordinary circumstances, strange and unsettling events begin to unfold globally.Would the genre of the world also become Fantasy or would it stay exclusive to him?

In his past life, Ethan Steele was an ordinary man living in a modern world—working a dead-end job, struggling through the monotony of daily life, and haunted by regrets of missed opportunities.At the age of 23, his life came to a sudden, unexpected end in a car accident. As his consciousness faded into darkness, he was sure it was over.But fate had other plans. In the divine realm, the God of Fate watched over the balance of life and death.Ethan's untimely death was a mistake, an anomaly that diverged from the preordained path of his destiny. It wasn't yet his time to die, and so, the god decided to give him another chance.“You were meant for greater things, Ethan Steele,” the god's voice boomed. “To correct this error, I will reincarnate you in another world—one filled with magic, swords, kingdoms, and adventure. You shall be reborn, but you will not remember your past until the appointed time. There is, however, a... complication.”By divine error, the god accidentally bestowed Ethan with the Harem God System without having any idea about it.This system is a powerful, reality-bending system that would allow him to charm and seduce influential women to build his harem, growing in strength and power with each conquest.“Your memories of Earth will return on your seventh birthday. I hope you enjoy your life here in this world”And with that, Ethan's soul was transported to a new world.

In the early world of immortal cultivation, there was no physical cultivation among immortal cultivators. And a top bodybuilder who came from the earth has opened up a new path here and became the ancestor of physical training.

- Description from novelbuddy