Master of the End Times - Chapter 1037 - The Missing Realm Core

A 30-year-old NEET is reincarnated into the body of an otaku that choked to death on instant noodles. As he comes to grips with his new life, he realizes that this world is subtly different from Earth. The denizens of this world are far better looking, and this new world also possesses futuristic technology as well as mysterious Yin Yang masters!

Shi Jin once read a book. It was supposed to be about satisfying the desire for vengeance.

The main character, also named Shi Jin, was the sixth son of his harem-novel-protagonist-like father. All was well—while his father was alive. But after his death, Shi Jin’s five elder half-brothers tormented him, eventually leading to his death. The protagonist was reborn, determined to take revenge, and… the novel was discontinued.

That day, Shi Jin almost spat blood and dropped the book into a shredder. The next day, he died in a car accident. Somehow, when he came to, he had transmigrated into a teenager, a youth also called Shi Jin.

There was only one problem. His father had just died. His older brothers were about to torment him…

Shi Jin: Let’s eliminate my brothers’ hatred, my goal is to keep my life!

- Description from Novelupdates

“monarch of entropy” introduces a cosmic entity of immense power, whose eternal existence was once defined by passive observation. Everything changes when a surprising connection ignites a spark of curiosity and a yearning for interaction. As this King explores his evolving desires, his colossal abilities begin to influence realities on an unimaginable scale. This is the story of a powerful ruler's journey from detached observer to active participant, where every decision, no matter how small or whimsical, creates ripple effects across the multiverse, leading to a series of grand, and sometimes inconvenient, adventures.

I finally managed to kill the demon lord.