I'll Teach You, Marianne. - Chapter 600 - I Chose You From The Start

The opening of Pandora's Box changed the world, giving rise to an age of superhumans and monsters. Yet mankind was not safe from its own hubris, and in the end, it destroyed itself. It's the end of the world, but Sonya Chernovna has been given a chance for a redo. With her memories of the world to come and her deep hatred of the society that had risen out of Pandora's Light, Sonya sets out to change the future.Even if it means being the most heinous villain that ever lived.--Chapters release on Monday-Friday with side stories sprinkled throughout.

The NPC sets out on a journey to defeat the Demon Lord, joined by beautiful girls he meets along the way.---This is an NSFW story, so if you're under 18, turn back now, son. No NTR, and no full-on Yuri. There might be slight Yuri—like girls kissing and stuff during threesomes—but it's not that kind of Yuri where the girls fall in love with each other while in a relationship with the MC.---

“You mean that Prince Yu wants to marry me?”

“Exactly, young master, Prince Yu wants to marry you!”

“Hell no! Is he out of his mind? Even if woman is a rare species nowadays, as the prince, he could have a chance to marry one. Is it because he got excluded, or maybe he has sexual impotence, so he could only marry a man?”

“No, Prince Yu is charming, majestic, endowed with civil and martial virtues, and also in perfect health.”

“Then why would he marry me?”

“Maybe because of your reputation out there.”

“Reputation? Am I quite famous?”

“Of course. Young master, you’re far-famed.”

“Really? What did they say about me?”

“They said you are ugly, good-for-nothing, short-lived, a freak, with no morals, and shameless…”

…

- Description from Novelupdates

This is a world where humans, demons and mysterious beasts coexist.

Humans cultivate mysterious qi. Demons cultivate corporeal bodies. Mysterious beasts cultivate soul perception.

A legend says that in the middle of an endless rainforest, there are extremely powerful existences; they are called demon kings.

Some demon kings have a tyrannical corporeal body, some are experts in illusions.
Some demon kings are proficient in magic, some can even move mountains.
Some demon kings are able to sense things thousands of miles away.

These demon kings rarely appear in the human world. Even if they emerge in the human world, they would reincarnate in human form; assimilating with mankind while seeking to breakthrough realms…

- Description from Novelupdates