Arifureta Shokugyou de Sekai Saikyou (WN) - Chapter 80 — Declaration of War

Ji Huan’s parents both died in a traffic accident.
Unexpectedly, his older sister also meets the same fate.
Yet everything starts when he says “goodbye” for the last time.

Hunting monsters? Genetic comparison?
Ji Huan flees with his older sister’s posthumous child to his hometown, Bade Town.
The three Grandpa, grandson, and nephew all live interdependent days.
However, inside the swaddling clothes is not a human baby,
But a monster…

Black egg body, white ring eyes, red mouth.
A child, ah! Doesn’t he have two eyes and a mouth! Resembling an egg, he is Ji Huan’s cute nephew!

Vermilion tiled wall, white lotus pond, convalescent courtyard.
This entirely neatly handsome and elegant young man: Ah Jin.
However, he told Ji Huan about the secrets of the monsters and discreetly taught him.
Bade Town is also slowly being covered in monsters…

Or, the record of a small countryside monster’s growth.

- Description from Novelupdates

Ding![The Host has died!]A system message popped up in front of Nell's body after his last dying breath.Ding![Dark Evolution has been activated to absorb the death essence of the host.]And then he opened his eyes to find himself in the past right before the battle started.'Ah! Am I back to the past?'Ding![Please choose a partner to start the Dark Evolution process.][Partner Condition: Must be a living creature from the Monster category, not the Human category][Partner Gender has to be Female.]'Partner? A monster?'Nell's heart pounded in his chest, and he felt a cold sweat coming on.'A female monster?'

Tang Shaoyang, an orphan who dropped out of the middle school to fight on the street as he found out school was useless for a penniless orphan like him.

Tang Shaoyang dropped out of his school, fighting on the street, and made a name for himself. Berserker Tang from Youyouliucun.

Afterward, Dragon Wing triad recruited him and everything was good for him. Even though the public deemed him as a tumor of society, Tang Shaoyang was having a decent life. Until one day, everything changed as an absurd and strange game started.

[… Game starts! Stage one: Survival for The Fittest!]

After the game started, zombies appeared out of nowhere.

I became a scientist for an evil organization.…But I’m too competent.