Reborn: Earth Online - Chapter 57 - 58: Maw of the Sewers

The world that nurtured the civilization which reached the pinnacle of magic was on the verge of destruction.
The last survivor transmigrated to the past, when the magic civilization started growing, as countless mages were still fumbling their ways through the thorny paths of magic knowledge.
He, who came from the end of the magic era, aim to reach the pinnacle of magic.

- Description from Novelupdates

What would happen when someone from our world was suddenly reborn into the world of My Hero Academia with a Gacha System that rewards him with abilities, techniques, and skills from Jujutsu Kaisen? Grand epic fights and crazy shenanigans as he goes through the story to cause chaos and change the world to his liking.

Content Warning: R-18, Smut, Cruel MC[Ding! You've acquired the Heroine Stealing System!][Your first task is to steal the daughter of the Eastern Kingdom's king!][Your Fate Value has increased by 10!][You've slept with the hero's mother, your Fate Value has increased by 15!][The hero has developed animosity towards you. Current Hatred Level: 5 stars][The king's wife is charmed by your looks.]After being transported from his own world, the protagonist wakes up as Vritra, the son of Demon King Rohan from the Hell Continent.Since he's from another world, he doesn't have any Fate Value in this new world of swords and magic.To survive, he has to act like a villain, stealing the affection of every hero's heroine and sleeping with them.This will boost his Fate Value and help him stay alive in a world filled with wars and political conflicts!

Gu Bai always believed that the stupidest thing he had ever done was listening to his bestie’s words of becoming a stallion genre novel writer, the most frustrating thing was that he changed the moral, smart, and healthy youngster, that he had decided on, into a big boss…but in the end, he discovered that the consequences of changing the original plot were more serious than he expected. Things like encountering the outrageous character he wrote with his own hand…

Oh·my·god! He freaking eats people! Right now, he can only turn devouring people into “devouring” people… maybe.

In short, this is a story about a dumb author who was the first to start a trend of human cannibalism in stallion genre novels, who in the end, was unable to escape from the whirlpool of destiny (not really).

- Description from Novelupdates