You are a part of the StrawHat crew, you can choose your own character, whether that’s one of the StrawHats or your own OC. You can also decide which time arc you’re in. Like for example, the SkyPiea arc, Luffy, Zoro, Sanji, Nami, Usopp, Chopper and Robin are the only ones on the crew at that point and the Going Merry is the current ship.

It’s a normal day on the crew, everybody is entranced doing their own thing. (You can make up your own scenario.)