One Piece: Don't Worry, I'm a Doctor - Chapter 15 - : Are You Crazy?

Finding an ancient treasure was not as fortunate as one might expect. As soon as Bai Rouyun had left the grave, countless sects and hidden families set out to kill her for the sake of obtaining her treasure for themselves.

Shao Xuan joins a friend in his expedition to a recently discovered archaeological cave. After he picks up an ordinary looking stone he is teleported to a different world and wakes up in the body of a small orphan child. The world he is in now is still in its stone age with primitive tools made of stone and the ways of the people are savage. Savage isn’t the only thing special about the people though, because they have superhuman strength, jump higher than trees and punch stones. In short, they are able to cultivate their bodies. Despite all this, it is a real struggle to survive because of the scarcity of food. Together with Caesar, his pet wolf, he tries to survive in this cruel world.

- Description from novelupdates

Shadow was an assassin with no family, no friends, and no purpose beyond the missions assigned to him. Kidnapped at the age of five and forced to serve a ruthless assassin organization for fifty long years, his life was a series of shadows and bloodshed. On the eve of his fifty-fifth birthday, he completed his final mission with hope in his heart. A hope that freedom and a better life were finally within reach.But that hope was shattered. Betrayed by the very organization he had devoted his life to, Shadow was ruthlessly killed, his decades of loyalty repaid with treachery. As his life slipped away, he swore one thing.“If he had a second chance, he would live life on his terms, unshackled and free”.In the void between life and death, Shadow's soul was met by “Syl”. The enigmatic Shadow Monarch's System. Syl offered him what he craved most. Another chance at life, but in a world far different from his own. Without hesitation, Shadow accepted, eager to grasp the life he was denied.Reborn into a realm of gods, magic, and chaos, Shadow soon learns the truth.He is a Wild Card, a pawn in the gods’ celestial game. Amere source of entertainment for their whims. But Shadow is no ordinary human. With the sarcastic and unpredictable Syl by his side, a glitching system that grants him powers beyond imagination, he embarks on a journey to defy the gods and forge his destiny.

Ron finds himself reborn in the world of One Piece, stranded on a remote island in the East Blue. But he's not just any ordinary child—he’s bonded to a mysterious sign-in system that grants him powers with every new location he visits.At his first sign-in, he unlocks the legendary Sun Breathing Technique, along with a boost to his vitality. From Shitmotsuki Village to Skypiea, Enies Lobby to Marineford, Ron travels the world, collecting extraordinary rewards that make him a force to be reckoned with. The Raikiri, one of the 21 Great Grade Swords, Armament Haki, Observation Haki, and more fall into his hands.As Ron steps onto the battlefield of Marineford during the legendary Summit War, the mightiest warriors—Four Emperors and Marine Admirals alike—pause, stunned by his presence. But Ron merely waves them off, “Don’t mind me. I’m just passing through.”Join Ron on his journey across the Grand Line as he signs in at iconic locations, growing stronger with every step. This is not just an adventure—it’s a legend in the making.