Valhalla Saga - Chapter 185

A War Without Casualties.The Republic of San Magnolia has long been under attack from the neighbouring Giadian Empire’s army of unmanned drones known as the Legion. After years of painstaking research, the Republic finally developed autonomous drones of their own, turning the one-sided struggle into a war without casualties-or at least, that’s what the government claims.In truth, there is no such thing as a bloodless war. Beyond the fortified walls protecting the eighty-five Republic territories lies the “nonexistent” Eighty-Sixth Sector. The young men and women of this forsaken land are branded the Eighty-Six and, stripped of their humanity, pilot the “unmanned” weapons into battle…Shin is the leader of a squadron of eighty-sixers. Lena is a “handler” who commands the detachment from the remote rear with the help of special communication technology.The farewell story of the severe and sad struggle of these two begins!

Damien Julian is an 18-year-old loser, who has been bullied and mistreated his entire life, at home, he has to deal with his abusive father, and at school, he is constantly been bullied by delinquents, and to make things worse he is always looked down upon by his peers, till one day a mysterious screen appear before him as it said.

[The world has seen the lingering evil in your heart]

[Would you like to be one of the nine demon kings of this world]

[If so what are you willing to sacrifice?]

In the heat of the moment, Damien made a deal with the world, that he would give up everything he owns, or do anything it wants, and in exchange, he shall be reborn as a new Demon King, and what the world required from him as payment was.

[In exchange for power, become a slave of the world, and act as an anti-body for all eternity]

At that moment, Damien agreed, but little did Damien know, that becoming a slave to the world meant he has to be its immune system, what that entail is, that anything that threaten the world must be destroyed even if he has to wipe out humanity, to save it, or assassinate historical figures to bring fort balance or even manipulating events that can potentially end the world, to save the world, this is the story of a necessary evil, not the story of a hero who cares for others.

The leaves of the chess game beside Lanke, and there is no one playing chess among the old trees
Xing caused Tian Yuan’s first son, and then looked back at the vast mountains and seas
When he woke up, Ji Yuan became a half-blind beggar in a dilapidated mountain temple.
A real person has a sword and a magic stick has a mouth, which is the foundation for Ji Yuan to settle down in this terrifying world.

- Description from novelbuddy

Crossing to One Piece world, he became Roger’s younger brother.