MTL - Rebirth of the Wolfish Silkpants Bottom - Chapter 46

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

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.

The world is governed by the Seven Legendary Heroes, their authority absolute and unchallenged even by their own descendants. They manipulate the world and its people according to their whims.Jonan, son of one of these legendary heroes, discovers his affinity with crystals and mastery over flames, yet lacks skill with weapons, which brings shame upon his family. As he delves deeper into the dark secrets connecting the heroes' power to the rifts and an ancient evil lurking, waiting for the right time, Jonan must move forward with unwavering determination.