In One Piece Odyssey Luffy’s experience and skills will be taken from him. In order to get them back, you’ll need to locate 50 cube fragments scattered around Waford Island. Below is a guide on where to find his cube fragments in Marineford. You’ll receive the Cube Collector: Luffy trophy/achievement for finding all of his cube fragments.
Marineford City Area
North Town
When leaving Gunpowder Storehouse and transitioning into North Town, follow the street south and head down a flight of stairs. At the bottom, immediately turn right. Take another right to find the cube on the side of the building.