The Rational Detective in Detective Conan - Chapter 26: The 10% Discount

The World was thrown into chaos with the arrival of monsters but the humans were given a chance of awakening powers.The MC who was once used to read stories like that was now reincarnated in such world.This is his story on how he would proceed in this troublesome world.

This is a story about a badass,

He became Arthur. He lived his life as Arthur and claimed Excalibur.Now, he has returned with a purpose.Beneath the surface of the world lies a twisted world known as the veil—an dimension where monsters are born from corrupted human emotions and desire. The deeper you go, the more terrifying they become.Each Layer is sealed. Each hides a god-like being, waiting to rise to the surface.Now, Sylas bears the responsibility of keeping the gate between both worlds from breaking.[Keys are passed down through generations.No one knows where they came from, but those keys can open doors to another world — a world filled with deadly trials. If you complete the trial, you return with blessings from gods, mythical beasts, and ancient warriors. The amount of blessings you earn depends on how well you perform.But if you fail, the door shatters… and you are gone forever.If you survive, you are given a permanent rank — a rank that decides your place in society for the rest of your life.]

What was originally an ordinary day, suddenly became a historical turning point. Enormous, mysterious Cubes appeared all over the world without warning and as if Judgement Day’s spears, inserted themselves into the blue planet.

From inside the enormous Cubes, endless streams of monsters gushed out alike raging tides, utterly defeating the unguarded armies of each state in the blink of an eye.

In order for humanity to preserve its final embers, the heads of states issued orders of retreat, to no longer attack the Cubes but rather to cling to remote cities, which they turned into self-sufficient survivor bases and around which they built 100-meter-tall Walls of Life!

Many years later, while bearing the heavy weight of history, the first expeditionary force brought back a world changing piece of information. The Cubes possessed exceedingly high intelligence and they regularly transmitted mission instructions to humans nearby. The mission rewards were incredible.

Since then, humans rushed out of the confines of the walls and once more set foot on the wasteland!

- Description from Novelupdates