Maou-sama no Machizukuri! ~Saikyou no Danjon wa Kindai Toshi~ - Volume 10 prologue

Instead of struggling meaninglessly, he acknowledged his place.

Felix Ariel, a typical Floridian, found himself transported to a mysterious kingdom in another world. However, a misunderstanding led to Felix accidentally killing the king, resulting in his untimely demise.Following this tragic event, Felix's spirit encountered a mysterious being who identified as Felix's ancestor. This entity claimed that Felix had been cursed by an unknown individual. For Felix's safety, the ancestor bestowed upon him a system for self-defense.Upon returning to Earth, Felix realized that he would be transmigrated to the alternate world at noon due to the lingering curse. To prepare for this unexpected transmigration, Felix relied on the system, which required him to gather oil and gold to enhance his abilities.Thus began Felix's quest in the other world. With his system, he brought firearms and an ambition to spread liberty... for prosperity and freedom.

Bai Yu traveled to the world of One Piece and activated the strongest swordsman system at the beginning.

No need to practice, swinging a knife will become stronger!

Thus, Bai Yu started his daily routine of wielding a knife.

Swing the knife 1000 times, and get the limit of physical strength – six styles.

Swing the knife 2,000 times to obtain the powerful Qinglong Sword Intent.

Swing the knife 3000 times, get three-color domineering.

General Huang Yuan: Bai Yu is the strongest rookie I have ever seen.

General Aokiji: My freezing ability was directly chopped into pieces by Bai Yu!

General Red Dog: Dangerous! My marshal position is about to change!

Hawkeye: Bai Yu is the number one swordsman in the world!

Since then, the name of Bai Yu has resounded throughout the world of pirates.

- Description from novelbuddy

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