Episode 0 serves as a tutorial stage, taking place just after the time skip in the manga/anime. The setting is Sabaody Archipelago and the Straw Hat crew are heading to The Thousand Sunny to begin sailing to the Grand Line. Of course, trouble finds them as the Marines have deployed Pacifista units.
When the episode starts, you are thrown into action by watching a cutscene, with some Quick Time Events (QTEs) thrown into the mix. The first two are pressing Square, then the third is rotating the left analog stick. When Luffy lands on the island with the Marines, there will be a few more QTEs, which involve pressing Square a few times and then mashing it twice.
Once those are over, you will be fighting some Marines. Familiarize yourself with the controls and follow the on-screen prompts to do the moves. Once you do the move with the Circle button, you will need to use various moves to defeat Marines until a cutscene occurs, where the Pacifista arrives. There will be one QTE here that involves X.
Now begins your first boss fight, which is against the Pacifista. He doesn't have too many attacks, as most of them involve shooting lasers of some kind. One to watch out for is a hand laser that he sweeps along the ground, but you won't get hit as long as you're behind him. Keeping attacking him with various attacks, including Luffy's special move (Circle) when the gauge is full.
Once you get his health to the halfway point, the Pacifista will unleash a special attack where he just shoots a bunch of lasers at the ground. When that's over continue attacking him until he hunches over and you get a R1 prompt next to him. This will trigger a special cutscene with two rather quick QTEs (Left analog stick down + X, then holding down both analog sticks). Once that is over, deplete the rest of his health to begin the final QTE event (X, then mash Square, ending with Circle). The battle is over, and so is the episode.
