Just don't ask me about Pirate Warriors 4, I will cry

imo Pirate Warriors 3 is good, but absolutely only EVER buy it on sale at the deepest of discounts, because the PC version is busted and prone to Crashes.
or if you have a console, that is just as Good. It's by the Dynasty Warriors/Musou Guys at Omega Force/Koei, where the primary Gameplay loop is running around a field, and pressing action combos to kill armies of guys.  They mix things up a lot with the One Piece version though, each Pirate you play as can do a "Buddy Move" with any pirate you have on your team, but some are more powerful than others. So if you already know the relationships between certain characters then you'll know what to expect.  It covers the story of One Piece very broadly up to a certain point, but once you've played the Campaign in full, you'll know all of the "Best Parts" One Piece fans enjoy the series for. With highly detained environment designs, amazing character Animations, and shockingly AWESOME Music that makes me with I had a CD with every track on it, so that I could have One Piece Dreams while I listen to it at bedtime.  there are some parts that are better experienced in the Book and Anime, but you wont be spoiled too hard if you'd see a particular part and decide "I want to know more about this Impel Down place" you'll have little enough context to still enjoy yourself after the fact with the source material.
Character customization is nonexistent, but you do get to pick and choose "hero skills" which are slowly unlocked as you play, and these are more like cheat codes that can make the game slightly easier for you if needed.  One possible issue you may run into is that this type of game is considered 'repetitive' since your character's strongest combo is always going to be something like :square: :square: :square: :square: :triangle: , in between running around and hitting Circle to Summon your Buddy for an Assist attack.  This is a shallow interpretation of the input system imo, since certain characters have different combo styles, and different input timings.  I like playing as Nico Robin for example because her Input rhythm has a delay that allows you to cancel out of combos to adjust to on the fly changes in the battle field, and her powers are more reliant on planned positioning than some of the other 'fight guy' characters.  I also like playing as Sanji who has a 100% debuff against women, so you have to get really creative with the mechanics to defeat certain enemies he literally cannot touch.
if you can wrap your bran around the Gameplay, it's a fairly chunky game to sink your teeth into, especially if you manage to get a copy for the lowest possible price.  In addition to the StrawHat Crew who are the main characters, you can also unlock access to dozens of other Enemy Pirates and other various Allies to the Strawhats. despite the play style, there is a ton of variety to be found in each character from their own individual combo rhythms to the tons of unique animations. and a lot of fun can also be found is taking characters from entire different parts of the story and running them through an era they don't belong to.  I haven't 100% the game yet, but I get excited to see what else the game has to offer on this front, and I rest easy knowing that there's probably a pirate that I have yet to unlock the full powers of yet (giving me an excuse to replay the story mode, because a lot of leveling up is tied to Golden Pirate Coins, which are coins you only gain from interacting with or Defeating specific characters)
it's been a long time since it's been possible for me to do so, but the Multiplayer is also very cool. You can get someone at your house to play in split screen mode, or if you're on PSN you ca play online with others that way. I'm not joking about the PC version being busted though, you will get insanely frustrated if you play it on PC, it shouldn't even be sold, but I suppose they think since it worked flawlessly at one point n the past, there's no reason to not keep selling it. Unfortunately the cocktail of reliance of Windows Media Playback for the cutscenes and the game running out of Memory during moments when Whitebeard is on screen and crashing don't make it worth even the $4 it frequently goes on sale for. But despite that, it's a Video Game experience that I think everyone should have at least once in their lifetime. between it's laid back mechanics and brain wrinkle puzzles and the big meat size of it all, it's one of the best games they've ever made. Which, now that I think about it - Koei is kind of like, the best Games Publisher ever? They're always trying new things, and take a very "if it ain't broke" stance of things that always work. I don't know much about their development environment, but their games seem to peak and valley in terms of complexity from the amount of stuff you have access to for your play time, to the overall density of visual detail. I'd own more of their games if they could just decide on a price scheme that works for a cheap bastard like me (Never pay full price for a Video Game) and Koei Games don't go on sale all that often.