Tensei Shitara Slime Datta Ken (WN) - Chapter 300

Follow Chen Ming as he accepts disciples, establishes a sect, and fights his way in a world that deems him a cannon fodder.
He goes against any common sense using his wits and novel knowhow to finish missions and arm himself against his cruel fate.

- Description from Novelupdates

She breaks all the rules.When master thief Xavier Valentine died, he caught the attention of Calypso, the Goddess of Reincarnation who turned death into her personal gameshow. But rather than simply send him to a new life, she made an unprecedented choice:She followed him in.Now trapped in a world of magic until seven Primordial Gates are cleared, Calypso and Xavier form an unlikely alliance. He needs to level up to survive. She needs entertainment to stay sane. The prestigious Catalyst Academy needs them to stop causing chaos for five minutes.They're probably going to disappoint everyone.In a world where dungeons hold divine secrets and ancient gates lead to untold power, one thing is certain:This goddess isn't letting her favorite soul leave her alone.

Martial Arts Year 1. Cracks have appeared between Heaven and Earth, and terrifying foreign monsters have begun to invade the earth.

Martial Arts Year 100. Martial arts have begun to flourish, and human martial artists are clashing against the invading foreign monsters.

Martial Arts Year 200. Humanity is declining, foreign monsters are continuously seizing habitual zones.

Martial Arts Year 300. Lu Sheng crossed over. Moreover, he had access to memories from 10,000 years in the future.

“The Body Refining Technique from 10,000 years in the future. After more than 10,000 revisions, it’s a thousand times more effective than the one used now!”

“Martial Art Breathing Method from 10,000 years in the future…”

“Medicinal Pill Recipes from 10,000 years in the future…”

“The Sacred Martial Scriptures from 10,000 years in the future…”

Martial Arts Year 10,000. Humanity has gone extinct.

“The Path of Martial Arts had been honed to its pinnacle, yet there was no one left to inherit it.”

“I, Luo Sheng, am Humanity’s final Ember!”

The world has turned into a hell, a place where the strong thrive!