One Piece Odyssey is far from the first turn-based JRPG based on Eichiro Oda's immensely popular manga and anime series, but it has proven itself to be the best and biggest so far, even when compared to the many similar games in the genre.
Like plenty of other anime-based games, One Piece Odyssey has an original story with a few game original characters and a new setting, all not previously seen in any other media. Because of this, there are quite a few aspects of the game that don't make sense, despite how wacky the series can be at times.
8 Time Placement
A common problem with anime-based games and movies is that their events are hard to place in the series, despite not being canon. In several One Piece movies, the original characters introduced are canon, but the events in each film are not. It's currently unclear whether those rules apply to recent games.
Odyssey takes place sometime between the Dressrosa and Whole Cake Island arcs. However, the crew had split in half during the Dressrosa arc, with some fleeing to Zou and others staying to assist the revolt. The entire crew wasn't on the ship together again until after the Wano arc, so it can't be placed where it's supposed to be.
7 Where Are The Other Members Of The Ninja-Pirate-Mink-Samurai Alliance?
If Odyssey does take place between the Dressrosa and Whole Cake Island arcs, then a few of the Straw Hat Pirates' allies are missing. Momonosuke went to Zou with that half of the crew, while Trafalgar Law and Kin'emon stayed on Dressrosa to take care of their business there.
Once the rest of the crew arrived at Zou, it was the first time they had all been together since the Dressrosa arc, with Law also having reunited with his own crew. Including these characters could have helped the game have even more One Piece flair, with Kin'emon providing the available alternate outfits and Kanjuro providing hilarious mounts for faster traversal in some areas.
6 Luffy's Trouble Fighting Animals
During the two-year time skip, Luffy trained his various abilities, including his Conqueror's Haki, by fighting animals on the island of Rusukaina, known for their ferociousness. When first encountering unfriendly animals on Waford, he doesn't even attempt to use this skill to scare them off.
Since the first boss, Del Kong, was introduced in the One Piece: Strong World movie, which takes place before the time skip, Luffy could have easily shattered its will to fight by using his Conqueror's Haki by the time of Odyssey. However, this probably doesn't happen because the game is still teaching you mechanics at this point, although it's still weird that he doesn't even try to use it.
5 Usopp's Lack Of Observation Haki
Luffy can use his Observation Haki to find hidden objects, but Usopp cannot despite awakening his in Dressrosa while protecting his allies. In the manga's canon, Usopp hasn't used this ability since, but in the non-canon movie One Piece: Film Red, he has honed this skill enough to communicate with his father, Yassop, from far away.
Since Odyssey is set after Dressrosa but before Wano and One Piece Film: Red, it could have had Usopp learning how to improve his Observation Haki. Even if the game's events aren't canon, going from awakening this ability to communicating with it is a giant leap, so seeing what it would be like in between would be interesting.
4 Nobody Ever Learned Pell Was Alive
During the Alabasta arc, a character named Pell seemingly sacrificed himself to save the desert kingdom. Later, it's revealed that he's still alive, but in Odyssey, Nami vaguely mentions someone who had died during their time there.
Characters rarely die in One Piece unless in a flashback, and when they do, it's rather significant. But somehow, during the entire two-year time skip, none of the Straw Hat Pirates learned that Pell was okay. It makes sense for some of them, since they likely wouldn't be reading the newspaper, but Pell's former enemy Robin could have known since the Revolutionaries do pay attention to the newspaper and other goings-on.
3 Lim's Powers
Lim's powers allow her to seal people's various abilities into cubes, making them forget how to use them. Smaller cubes can be absorbed by who they previously belonged to, while larger cubes require Lim to send them into a memory world called a Memoria to redo previously completed tasks.
Some of these powers' rules don't make sense. Characters don't wear their previous outfits, despite everyone else seeing them that way. Since memory can be hazy, some details aren't exact, but creatures the crew hasn't seen, such as the game original Kaio Dragon, shouldn't be there. Finally, if a person dies in a Memoria, their body becomes a lifeless husk, which is seemingly irreversible, but how did Lim learn this?
2 Adio's Powers
Adio has the powers of the Grab-Grab Fruit, which allows him to pick up and control non-living things using giant projected gauntlets. While it's an interesting power, its details aren't explained quite as much as those of previous original characters.
Since he can use these powers to block or grab nearly anything and has been on Waford for a while, you would think he'd have more techniques at his disposal and would've awakened his powers to help him explore and perhaps even get off the island, but he was too obsessed with getting revenge on the World Government a different way.
1 Adio's Background
Late in the game, it's revealed that Adio is the last living member of an ancient tribe of Waford, which was once a sky island like Skypeia. For someone with such significance in the game and is related to one of the series' most crucial areas, you'd think Adio's background would be expanded more, especially with how often character backgrounds are fleshed out.
According to Lim, Adio is incredibly lonely despite his usually cheerful demeanor, but it seems as if he never even tried that hard to escape Waford and find an alternate life path. His hatred toward the World Government could've led him to join the Revolutionaries or become a pirate after successfully escaping.