Blacksmith of the Apocalypse - Chapter 4 - 4. Grinding!

A girl who calls herself a demon appeared before a timid student named Fumio Kijima. The girl claims to be a campaign girl from the demon world and she gives him the ability to “summon a room” from nothing but thin air.

At first he doesn’t abuse his power and uses it as a convenient ability in his every day life. But one day he is bullied by his classmates under a false pretext and is made to suffer. In the past he would have wallowed in misery and cried himself to sleep, but now he had a power to call upon.

“I will make them regret it!”

Using his powers to summon his “room”, he begins his era of confinement and brainwashing to achieve his goals.

You Liangxing would never open the speech function in game.
That was because his voice was…
Particularly! Kittenish!

But there was one day, he queued up with a teammate who had so much to say that they may as well explode. Vexed to the point of no return, he contributed a voice that was capable of splitting heaven and earth, “Don’t BB.”
The other party who was being scolded stilled. In the ensuing silence, he suddenly let out a long, relishing… Moan.
You Liangxing: “…..”

Later —
He realised that the person was a great god,
Much later,
Without him realising,
He became the great god’s royal healer.
…. And also his boyfriend.

- Description from Novelupdates

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

Originally born from a wealthy family, she ends up leading a vagrant life for fifteen years. However, when she is eventually found by her family, she falls into another devious plot and eventually dies tragically.

Fifteen years after her rebirth, ravenously raging for revenge, she tears down the hypocritical mask of the foster daughter who had taken her place, and reduces her greedy stepmother and stepsister back to their original sorry states.

To the jerk’s profession of his deep love for her, she only has one thing to say, “Get the hell out of my life. The love you speak of humiliates love!”

Regardless of the appearances of you monsters, I’ll take in it my stride with my capability, building a business dynasty of my own, sitting in the depths of my riches, bathing in the glistening limelight of the world.

A certain rich empire’s CEO: “Don’t mind me. I’m just leaving my mark here to declaring my possession rights; I’ll wait patiently for you to grow up!” The queen’s mighty return with commercial warfare fully within her grasp, she navigates the power struggles with skill and verve. When it comes to scheming conspiracies, all she has to say is, “Who are you again? Don’t even bother!”

- Description from Novelupdates