The World I Rule

It's been a while since Chido felt like he was at the top of the world. He was untouchable in high school, but now... he's barely eking out a living by being a delivery boy. Frustrated at his lack of power, he yearns to find a way out of his humiliating life. On a particularly tiresome day, he encounters an earthquake on his way home and gets sucked into a whirlpool. When he opens his eyes, he finds himself in an unfamiliar island with strange, sexy natives who do not seems to speak any language he knows. They seem friendly enough, and it looks like Chido can make them do anything that he wants. Absolutely anything.

Original Webtoon

Official Translations:
English (Lezhin X, Lezhin US), Japanese

The protagonist is sucked in to a weird whirlpool in a river and somehow ends up in a island in another world with native elves that wear leaf clothes, have the knowledge of an new born, and have sex like rabbits. That also have a body as weak as butter.
He decides to become the king of the place and rule with an iron fist and teach the naive elves cruelty, evil and watch as they kill each other.