Youkoso Jitsuryoku Shijou Shugi no Kyoushitsu e - Volume 15.5, Chapter 2 Intro - THE BEGINNING OF THE SHORT-LIVED VACATION

One day, Zhang Fan, a poor medical student, receives a medical system from the future. This turns him into a new shining star in the medical field. Along the way, he must face medical corruption, competition, and infighting from other doctors, and even find time for a love life as he strives for the top of the medical field!

- Description from Novelupdates

Before meeting Shen Xu, all Zhen Yuan wanted was to seek the dao and cultivate to the peak. After meeting Shen Xu, he thought the dao was important, but his wife was the most important.When Shen Xu transmigrated into a book, he mistakenly believed that Zhen Yuan was not a character in the original story. What he didn't expect was that his husband was the most mysterious and powerful unnamed character in the original novel.

“Marry me, and you might not live to regret it.”Everyone in the city knew about him—a ruthless tycoon with a dark reputation. Whispers said he was cursed, having outlived four fiancées, each meeting a tragic end. When she became the fifth, forced by her own father to take her sister’s place in the marriage, the city waited for the inevitable. They were certain her body would be carried out of his mansion within a month.But to everyone’s shock, not only did she survive—she thrived. From a pawn in a deadly game, she rose to become the most formidable woman in the city, turning the tables on fate and rewriting her destiny.

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