Little Prodigal Alliance Head (and Cook) - Chapter 4: Life Hanging By a Thread

Bored in class, Ivaim suddenly transmigrates into a world plagued with Fractured Realities.A century ago, Reality Masters suddenly arrived— bringing a wave of terror over the planet.Just as the people despaired, they began to discover “Threshold Items” which allowed them to enter the domains of these Reality Masters.They had two options starting from there :One, to become a Reality Walker— a person marked and blessed by a Reality Master, fighting by their side in order to defend against other Reality Masters.Or to become a Reality Ruiner— A person who kills Reality Masters, directly consuming and taking over the powers that they posses!However, to Ivaim, he seemed to have taken on a different path.As he looked towards his own body, he sighed as he realized that he was neither a Reality Walker, nor a Reality Ruiner.—He had somehow become a Reality Master....

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

Suzumiya Kaede, a gamer, fell asleep while playing a game all night and when he woke up he found himself in another world, a fantasy world where using magic is possible! Using his knowledge of games, skills, and cheats, Kaede decides to enjoy as much of his new life in a different world through his newly-acquired magic and sword!

No one is optimistic about the marriage between the most respectable man in Yun Cheng and the most disfavored daughter of the Mu family.