One Piece: So I’m Actually a Myriad Worlds Traveler

No promises, and I can't guarantee I won't drop it. I'm just writing whatever comes to mind because I'm bored. Basically, the protagonist gets a Destruction Dragonmon fruit that doesn't exist in the One Piece world, then happens to kill a transmigrator with a System. The System follows the principle of staying close by and possesses him again. From a perfect start in one world to a start across the myriad worlds!