MTL - The Upgrade System of All Realms Starts From Conquering Naruto - Chapter 12 Is this your answer?

Liola—the best assassin in his world—has vowed to kill no more. He was being chased by an assassination organization when he accidentally dropped into a parallel universe: through a dimensional gate and into poor teenager Kaiser’s apartment. Instead of going to the government shelter for lost dimensional travelers, Liola and Kaiser wind up going to school together.

Liola has been trying his best to live the life of an ordinary person, but after certain things happen one after the other, he begins to realize that being an ordinary person could be harder than being an assassin.

Mystery is the nourishment that keeps me from being ordinary.

It has been 20 years since he came to a world similar to the modern European background. With his early wisdom, Fei Lin learned a skill and finally became a decent person.

Originally thought that he would marry a wife and have children and live this life in a dull way, but found that there is another world under the shadow of the world.

In that world, there are occultists who practice esoteric techniques and master extraordinary powers.

It is weird to spy on humans in the dark and feed on humans.

There are evil god believers who worship the evil god, please the evil god through bloody sacrifices, and exchange power from the evil god.

There is an evil god who wanders outside the world, peeps at the world, and only infiltrates the power of scales and claws, which is enough to cause people to fall.

With the mystery as nourishment, he is no longer ordinary after 20 years of ordinary.

Living in this apocalyptic world full of zombies and monsters, the rich rely on technology and the poor rely on mutation.

Shen Shanwu, 13 years old in appearance but 31 years old in reality, is a mutant that can alter his own appearance. Although he looks like a child on the outside, his wisdom is not very good. One day, he was just passing by when he was suddenly forcibly adopted by a major general, whom he didn’t know where he came from.

He resisted, but when he looked up, it turned out to be an old acquaintance.

The little boy, who could only hide behind him and cry, transformed into the unsmiling, cold, and tough man in front of him. And that expression of seeing a dead beloved is really unsightly…

Shen Shanwu: Can you smile?

Jing Huan: After Shanwu died, I couldn’t smile anymore.

Shen Shanwu: …Who? Who do you think is dead?

It took a long time before he found out about it. He found Jiang Huan crying and holding Shen Shanwu’s nameplate in the middle of the night and told his adopted son how good Shen Shanwu was… All of this…was seen by Shen Shanwu himself!

Jiang Huan (raising his gun): Since you have seen my embarrassing side, then I can only marry you or kill you.

Shen Shanwu: …

Shen Shanwu: Marry, marry, marry! I will recruit 800 zombies to carry you home!

- Description from Novelupdates

Tired of the schemes and strifes of city life, Bei Feng finally returned to his hometown in the countryside

While picking asters ‘neath the Eastern fence;

My gaze upon the Southern mountain rests;

Rearing a few chickens and ducks, I shall lead a simple and leisurely life!

However, who would have thought that fate would play a huge joke on Bei Feng? All kinds of magical items and beings of the Myriad Worlds could actually be fished out of the Ancient Well in his yard!

Even a chicken reeled out of the well ended up chasing Bei Feng all over the yard and beating him black and blue! Speechless and aggrieved, he asked the Heavens: if, that day, he’d fished out a Dragon instead of a chicken, what would’ve happened to him!

- Description from Novelupdates