One Piece: Unreal Adventure - Chapter 43: Home Run

Qin Tian accidentally transmigrated into a sickly body, a body with broken Dantian that was unable to practice Qigong, in another world. Fortunately, God had mercy on him by giving him a level up system. Useless? That was him in the past. Not worrying about practicing Qigong, he was now able to kill Monsters to level up. Easy! Level up when killing Monsters; level up when killing people. An unbeatable sovereign of the clan in the eyes of other people, but in his eyes, he is a glittering big BOSS.

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

One day, a door to another dimension opened all over the world.

“Channel”

At the same time as the channel opens, different races appear on Earth, and mankind awakens its magical talent.

But…? Yoon Min-joon, was able to use magic long before the channel opened.

The forced escape of a reclusive loner who was once the only wizard on Earth.

“It’s dangerous outside the house.”

With the ability of the King of Silver, the first king in “K”, to be immortal and immortal, he crossed into the world of One Piece. Although he became a Pirate, he did not target One Piece.

His goal is to live freely on the sea, it’s that simple.

- Description from novelbuddy