Naruto System in One Piece - Chapter 477: Haruno Sakura’s Retention

In the aftermath of a tragic incident, the soul of Zhang Fei was transmigrated into a sacred body in a world of cultivation. Joined by the consciousness of an ancient cultivator, Zhang Fei must find a way to survive in this deadly world of beast demons and immortal cultivators.

In the City of Crime, one law stands above them all: Only the strongest can live.

A high school student that has lived as a mob-character ―― Mimori Touka

Chen Sha came to a world of immortal martial arts and was ordered to take charge of the world’s first sect.

Before his death, the previous chief told him:

“If you don’t become the best in the world for one day, you are not allowed to go down the mountain for one day.”

So he closed himself in painstakingly, crossed the heaven gate in his body, and faced off against the ancient and modern powerhouses…

…

Many years later, Chen Sha recalled the day he went down the mountain,

From the moment he descended the mountain, he was number one in the world.

In the next ten epochs, any gods and demons have returned, immortals and Buddhas have lived in the world, ancient powers and ancient gods have appeared one after another.

No matter how the times change, he has always been No. 1 in the world and has never changed.

- Description from novelbuddy