I Hate Systems - Chapter 1005: Inevitable Clash

Meet Sora and Shiro, a brother and sister who are loser shut-ins by normal standards. But these siblings don’t play by the rules of the “crappy game” that is average society. In the world of gaming, this genius pair reigns supreme, their invincible avatar so famous that it’s the stuff of urban legend. So when a young boy calling himself God summons the siblings to a fantastic alternate world where war is forbidden and all conflicts–even those involving national borders–are decided by the outcome of games, Sora and Shiro have pretty much hit the jackpot. But they soon learn that in this world, humanity, cornered and outnumbered by other species, survives within the confines of one city. Will Sora and Shiro, two failures at life, turn out to be the saviors of mankind? Let the games begin…

He rose from abjection and achieved eternity in glory.
He embraced the prettiest beauties and killed the strongest opponents.
He was able to shift the clouds into rain and cover the sky with one hand.
He could overrun the entire world and go anywhere as he pleased.
He pacified wars and held the world in awe.
He was matchless in the world.
However, his hair turned white overnight for his beloved woman and he was on the verge of death.
He was surrounded by enemies who were trying to take his life.
He struggled his way to become mighty and fought for everything he cherished.
For this age, he was the only king of the Dark World.
His name was a byword for might.
As a man living in the world, his only ideal was to pursue brilliance.

- Description from Novelupdates

Anastasia Harrison, a young woman abused by her cruel family, thought her life was over when they forced her to marry Richard, the sleazy black sheep of the wealthy Wallace family. Meanwhile, her favored younger sister, Michelle, was set to marry Xavier, the elder brother, who was a CEO.Yet, an error at city hall ended up swapping their names on their respective marriage certificates.“What is this?! How are you married to Xavier Wallace?”“You're not getting any food or water until you sign the divorce papers!”To add fuel to the fire, the old Mr. and Mrs. Harrison passed away, leaving all their assets to Anastasia and not the rest of the family. This drove the Harrisons to their breaking point. To trade for a peaceful life, Anastasia was willing to leave her inheritance and leave the family, but the Harrisons had other plans in mind.They wanted to get rid of her. Permanently.However, it was by a stroke of luck that Anastasia was found by her new husband, Xavier, before her family succeeded. Determined to get her revenge, she struck a deal with Xavier.“Continue to be my wife and I will help you get your revenge!”

A girl who calls herself a demon appeared before a timid student named Fumio Kijima. The girl claims to be a campaign girl from the demon world and she gives him the ability to “summon a room” from nothing but thin air.

At first he doesn’t abuse his power and uses it as a convenient ability in his every day life. But one day he is bullied by his classmates under a false pretext and is made to suffer. In the past he would have wallowed in misery and cried himself to sleep, but now he had a power to call upon.

“I will make them regret it!”

Using his powers to summon his “room”, he begins his era of confinement and brainwashing to achieve his goals.