One Piece: Pirate Warriors 4 is a combination of Dynasty Warriors franchise plus the One Piece lore. It features different arcs starting from the Alabasta Saga up until the Whole Cake Island arc. Thankfully it only selected some of the arcs and not all of them because it will take way too long to play, but at least they got to introduce some very important characters with compelling stories.
The gameplay is pretty much Dynasty Warriors with upgrades for unlocking different types of rapid button attacks, special attacks, increasing stats, and more. You fight against hundreds of soldiers while you alone defeat them in a couple of hits, satisfyingly blowing a lot of them away. You then meet particular characters and villains along the way where you can recruit them or defeat them depending on the situation. The early stages can be defeated without that much of upgrading and grinding of experience for levels, but later on, you would need to grind to increase your stats.
Depending on what character you are fond of, you can master that one and completely upgrade it to become the ultimate warrior. The problem is the other characters that you are forced to play on certain story missions. You do not have a choice and must try to complete that mission to move on. This is where you get to grind with previous missions, gain in-game money, and use that money on them to upgrade their stats. It is a pain to do, but a must if you want to go ahead of the story. Bosses tend to become difficult to handle at times, which is why you find ways to overcome that difficulty. It is a difficult task, but not impossible to do.
Since some arcs have been covered by previous titles already, I think it makes sense that One Piece: Pirate Warriors 4 skipped some of them to compact the story mode. It still packs a lot of emotions just like the anime and very engaging if you are a fan of the franchise. The game original Wano Arc though kind of stretches the story a bit, which made it a bit unbelievable and incomplete. Since the arc is still ongoing, it is the best thing they could do, but it should have been at least be a bit nearer to the material I guess? I will just give you a hint: fighting a big boss with the power of friendship and redemption. Yeah, it is that kind of a farfetched of an idea.
One Piece: Pirate Warriors 4 comes with all of your favorite background music tracks from the anime, which makes it all so nostalgic. As a guy who follows the manga and watches sometimes the anime, it is a pretty good game to play on with all of these nostalgic sounds. The voice-overs are quite good too and I think they got the original voice actors from the anime to do this.
Visually, One Piece: Pirate Warriors 4 looks okay for a 3D anime game. It just reminds you of the anime for some reason and the cutscenes are done well. It is also very colorful, which makes it not boring at all. In fact, it kind of makes you excited to play compared to some Warriors-like games with depressing, faded colors.
In its entirety, One Piece: Pirate Warriors 4 is a great game to play and grind because it is not boring, colorful, fun gameplay, and if you are a fan of the franchise, you will definitely love this. A must-have for the biggest fans of the series. Heck, I caught up with the story arcs I missed through this game.