My Lusty Wicked Degenerate System - Chapter 20: Teaching From Kind Godfather System

Zaria of the village of Latian. A former skilled mercenary with a strong, beautiful face and a tall, voluptuous body, she fell in love at first sight with the kind and gentle villager Albert, and since then has quit rough work and lived as a married woman devoted to him. It seemed as though their happy days would continue forever, but one day her husband Albert was injured at work, and he was barely able to stand or walk. To cover her immediate living expenses and her husband's medical expenses, Zaria uses her “previous job” to become a sword instructor for the son of a certain lord, but...

Have you ever thought that the state of the world as it presently is, could revert to the laws of the ancients? When a series of strange incidents beginning with the disappearance of his friend led Luo Yuan to question the possibility of an apocalypse, he becomes embroiled in the midst of a global-scale chaos.

Evolution has turned the flora and fauna of the vast and bountiful Earth into something that had never been seen before. Coincidentally, the all-dominating Homo sapiens have ended up at the bottom of the food chain. From mystery to crisis, will Luo Yuan discover a means of saving humanity by racing to the top of the food chain? Or will he strive in accordance with the law of the jungle? It is the dawn of an age of the survival of the fittest.

- Description from Novelupdates

Chu Mu Yun relied on his story of 《Demon Realm》 to become a one-hit wonder in JJWXC, but the him who had written seven mental cases to abuse seven mental cases to death would never have expected that he himself would transmigrate into this shitty novel!
What the hell is this system on the bracelet?
And what the hell is this either propose to seven men, or suffer the taste of a tragic death experience under the hands of these seven people?
I just wanted to write a novel to satisfy my bad interests, who would actually want to get tangled up with a bunch of mad dog sad*st crazies?

- Description from Novelupdates

This legend tells the tale of the protagonist, Kuroki summoned to protect the demon king from the hero.

Kuroki, unbeknownst to him, suddenly came to another world. He was summoned by the demon king, Modes. The territory which the demon king overrules was in the midst of being destroyed because of the hero. He had no choice but to bow before Kuroki.

“Please save us, Savior Dono!”

Kuroki nodded, deciding to save the demon king due to an unexpected turn of event.