Kyoukai Senjou no Horizon - Volume 2, Chapter 21: The Two in the Meeting Place

This is a cliché story about two young people saving the world.

The Mad Cultivator follows the tale of Ye Kong, a rude and vulgar thug from modern day China. While collecting protection fees, he was sent to another world! By the time he realized what was going on, he was possessing the body of an idiot. Watch as Ye Kong struggles against fate to climb the road to immortality!

- 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

The red meteor shower rained across the sky, a black fog engulfed the world.

After waking from a night of torture and agony,

Humans discovered they no longer dominated the world.

—The hunters have become the hunted.

After the apocalypse, I struggled for survival for ten bitter years, but ultimately couldn’t escape death.

But when I opened my eyes again, I had transformed from an ordinary 35-year old woman into a beautiful young man of 18.

A different gender, a world that is both familiar yet not, an apocalypse that has vanished without a trace, and an unexpected return of 17 years of youth.

Looking around, I discovered I had a powerful, protective big brother and a gentle, charming little sister.

Just as things couldn’t possibly look any brighter—

The end of the world came crashing down again.

And this time around, is it fight? Or flight?