Doctor's Rebirth - Chapter 44

Traveling to a parallel world where demons reawaken, Lin Heng becomes a Daoist and is tangled with the eerie Life-Buying Money.One day, ten years of life are borrowed, and as he faces the brink of extinction, fortunately, the system activates!“Fusion, Five Thunders Righteous Method!”With the Great Divine Techniques of the Celestial Master's Mansion in hand, Lin Heng awaits the eerie entities coming for his life that night.

The world that nurtured the civilization which reached the pinnacle of magic was on the verge of destruction.
The last survivor transmigrated to the past, when the magic civilization started growing, as countless mages were still fumbling their ways through the thorny paths of magic knowledge.
He, who came from the end of the magic era, aim to reach the pinnacle of magic.

- Description from Novelupdates

Lin Tian, who had reincarnated into the world of One Piece ten years ago met Garp, who was on duty to eradicate pirates, and become his student.

He, since childhood, had followed the Foreigner to practice the Defying Heaven Art, entering the most secretive special forces and becoming a fearsome assassin that made others tremble at the mere mention of his name. After a single failure, he took early retirement, but he ended up as the personal bodyguard for a rich heiress, a school beauty. Accidentally provoking some mysterious Cultivators, he gradually unveiled a hidden world of Cultivation beyond the mortal realm...