Netherborne [An OP Monster Isekai] - Chapter 45. Demon King

Xiao in his first life didn’t have the talent to reach the top and during his life he was killed by one of the heavenly Opposers, then he was born again in the second world where he again faced problems, after surviving and dying in the second world he was again brought back to as a child in his first life, this time Xiao swore to lay low, he would use his future knowledge to get cosy with the characters that would become strong in the future, he would lay low and try to become an immortal while fulfilling his desires but how did things get so bad??

Reincarnated Empress: Xiao's the only man in my life, he's the one who caused my ambition to bring down the heavenly court to dust!!

The Forsaken Heavenly Beast: Brother Xiao's the one who saved my life and gave me meaning, he's the one who gave me the courage to go against the heavenly court!!!

Succesor Of The Medicine King: Brother Xiao's my role model, he's a true man!!, he's the only one worthy to rule the heavens, he's our heavely opposer's leader, the opposing Emperor!!

The True Mc: Me and Xiao might not be related by blood but I am more than willing to lay my life down for him!!, he's the reason that the group heavenly opposer's even exist and we will bring down those stuck up rulers of the heaven!!

Xiao: “......”

He died on the wedding of the girl he had a crush on, after a long and successful career. After convincing Yama to send him back to the world, he decides to fix the areas in which his life went wrong. Realizing the lack of love and romance in his past life, he sets out to conquer the hearts of various women.

- Description from Novelupdates

Kai is the hardest working warrior in his generation... and the unluckiest. In a world where most people receive magical skills, classes, or cultivation, Kai has nothing but his wits and his strength. His only choice will be to forge a new path against fate, no matter where it takes him.

Savage monsters pour endlessly from the wasteland, threatening the survival of civilization itself. They say that human strength isn't enough and only those gifted with destined powers have a chance of making a difference. Kai is hungry to fight in that war, to be someone who matters. That hunger will take him across a world stranger and more terrible than he could possibly have imagined.