MTL - Marvel: Containment Foundation From Scratch - Chapter 56

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

Three thousand years ago, Bai Qiuran, who was extremely talented, was accepted as a disciple by the founder of Qingming Sect, and the young Taoist began to cultivate the path of immortality.

I don’t need any deep relationships. I have no desire for a girlfriend, and I only require one friend who holds any value to me. Ever since I threw out my youth for the sake of efficiency, there is one person who keeps entering the bedroom of Ooboshi Akiteru. She’s neither my little sister nor my friend. She’s nothing more than a bothersome, annoying Kouhai, as well as my friend’s little sister: Kohinata Iroha.

“Senpai, let’s go on a date~! Did you think I’d say that~?”

Rather than blood, it seems like energy drinks run through her veins. She keeps occupying my bed, and she tries her best to seduce me with whatever method she can play to her favor. She’s a girl who’s constantly annoying and obnoxious around me. Even though I’m busy all day long, she doesn’t care.

And in case you’re wondering why all these envious gazes are directed at me, it’s because Iroha is actually really popular. She’s an honor student at our school with top grades to boot, and she’s known for being kind and proper to anyone she meets.

…Hey now, why are you only so annoying when you’re around me?

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.