To be honest, Turbo, this fic hasn't improved much since you first posted it on Bulbagarden. You've managed to de-text wallify your chapters, I'll give you that, but IMO, it's still not a very good story. Things happen way too quickly with little to no explanation, which is a big flaw in many fics.
Please do try to add more substance to this story, I implore you.
I am heavily concerned about the state of Bulbagarden's fanfiction community if this is the kind of reviewing one of its mods pulls. :| If you'd rather call a story crap instead of giving the writer a constructive review that points out specific details, you're not helping anyone. You're just making the writer more inclined to either blow you off, blow
all reviewers off (which
has happened in the past when snarky reviewers -- who I'd like to keep nameless to avoid drama -- decided to flame a person instead of work with them), or stop writing altogether. In other words, you're not helping the community itself because you're not being a productive member within it.
With that being said, I have to admit I skimmed over the author's note at the beginning, Kaiser. The reason why is because if there's anything important contained within it, it should be brought up in the story itself, provided the narration is strong enough. In other words, it's more or less a test. (I'm not saying that you yourself are a weak storyteller just for having an author's note.)
I'm also not really touching on grammar, in part to warm up for the reviewing challenge and in part because I'm suffering a bout of laziness. I'll point out anything important, but if this ends up being a few short paragraphs about your characterization, plot, and use of language, I hope you'll still accept that.
And now... *knuckle cracks* The review proper.
...Which starts off right away on some concrit. I have to agree with Dragonite. It feels like a lot of this is rushing, so we're not really getting a good picture of what's going on. For example, if an attack just happened, what kind of damage are we looking at? Are buildings leveled? Are bodies everywhere? Are there still stragglers, or did
all of the Heartless and Team Rocket just up and leave? If it's the latter, why did they attack the village and leave it without a few remaining soldiers to hold the metaphorical fort?
Then, there's a couple of nitpicks I have about that first line. First off, if this is taking place in Sinnoh, why is Team Rocket there? Sinnoh is Galactic turf, after all, and even in the anime, Team Rocket had never established a proper foothold in that region. That's why Jessie and James were sent there (besides to spy on Galactic's activities). I'm just asking because it seems like a lot of people, when they want an evil team, either use Team Rocket or make Team Galactic/Magma/Aqua seem exactly like Rocket.
On top of that, while I understand Kingdom Hearts fans would automatically know what a Heartless is, you could use some description of them (and Team Rocket, for that matter) somewhere in here. I mean, you're doing what's practically an in medias res, so rather than summarize what happened that led to Barry and Paul going there, it might be a wise idea to show us what went down. Show us the creatures/Team Rocket attacking the village and how they did it. Give us some visuals (i.e., imagery) to help us develop some mental image of what's going on. If you start off by describing the battle itself, you'll actually start off on a stronger note because action = exciting to a reader. In other words, if you make your beginning seem exciting by showing instead of merely summarizing, you'll draw more readers in because they'll think to themselves, "Wow. This fic is awesome! Stuff's happening already!"
Dialogue's a bit tricky to puncutate, and although I could go into the rules, that would take up a lot of time. What I'll do instead is just show you
this guide and tell you that, yes, proper dialogue writing
can make a difference in how the quote comes off. For example, attempting to use one dialogue tag for two different sentences like you did with Paul's first line causes the entire quote to read as if it's only a single sentence. As in, you're implying that his first line reads as: "Umm.. Yes it is oh no! I see somebody lying there right next to Mewtwo!" This is because there's no proper punctuation between both halves of his line, and one dialogue tag is trying to merge the two sentences together. A dialogue tag is only tied to one half of the quote or the other. Once you tie it to one or the other, it's automatically implied that the rest of the line goes with the tag as well.
Which brings up another thing. Whenever you change speakers, you
need to start a new paragraph. For example, Barry's line just before the part I quoted above goes in one paragraph, but Paul's needs to go in a completely separate one. I say "needs" here not only because it's grammatically correct if you do but also because that helps clarify who's speaking each part of the quote once you separate Paul's properly.
Moving on, also agreed with Dragonite. Mewtwo seems to show up randomly, and that's a bit jarring as well as baffling. You don't really explain why Mewtwo is there; it just shows up out of nowhere. What's stranger is that neither of the characters comment on the fact that Mewtwo is there. If we're going by anime canon (which I assume so because you're using Paul here), they shouldn't even know what it
is, so it strikes me as strange that they just sort of shrug it off and pay attention to only Eric.
Meanwhile, remember what I said earlier about why I skimmed the author's notes? Here's where it comes into play. We still don't know who Eric and Kiki are. You don't describe Eric (despite the fact that you had a perfect opportunity if you went into description of what Paul and Barry were seeing on the island), and although it would make sense for Eric to call Kiki by her name, we're not really given any description of what he's seeing around him and what he's thinking, which would provide a perfect place to mention that Kiki is his girlfriend. As a result, if the reader doesn't read the author's note, we just don't know who Eric and Kiki are at all, and that's a bad thing because, as I've said, these are the sorts of things you should actually bring up in the story proper to have a strong story. Don't rely on author's notes to tell the story for you.
(Yes, I realize that you describe Eric later, but it comes several paragraphs too late. As a result, it feels like it's just stuck in there when it should have been more appropriate right around the part where Barry and Paul discover him and the reader first gets a glimpse of him.)
Side note, by why would Arceus have no problem with Team Snagem? They're a group of petty thieves who aligned themselves with Cipher, after all. Also, the Pokémon Rangers are not a team a la Team Rocket. It's an actual occupation, more like trainers.
...Why was Mewtwo there if all it did was sit there, watch over Eric, and teleport away? It seems strange because, well, it could have been any other Pokémon that did that job for Arceus. Mewtwo, meanwhile, was a legendary that not many people in the anime canon know about. So, it ends up being a little weird because no one comments on the fact that it's there, and it doesn't even really do anything ground-shakingly important before teleporting away.
While we're on the subject of plot holes, how does Eric know that Kiki is still alive, even though he has no idea where she is?
Also, what king? While I understand this is a Kingdom Hearts crossover, there isn't a king in Pokémon canon, which is where Barry and Paul are from. (Well, no modern-day kings of the entirety of Sinnoh, anyway.) Because of that, you'll want to explain a bit more about who sent Barry and Paul and what sort of differences there are between the Pokémon world we're used to and the one you're using, just so we, the readers, can have a better grasp on what's going on.
Furthermore, how did they know the first portal would be in the Battle Zone?
Going into chapter two, all I can say from the get-go is that Barry's reaction to his father's disappearance feels a little wooden. He doesn't stop short. He doesn't question whether or not it's true. He doesn't react to it emotionally (through body language or just the way he says things). He just yells into the sky and continues on as if barely anything has happened. I mean, if you were told one of your parents disappeared, how would you react to that? Try to base how your characters react on how people in real life would. Think about what the people you know would do. Generally think of your characters as
people, and you'll be more likely to make them believable and interesting.
How does Paul, who's lived in Sinnoh all his life and never actually encountered Team Rocket besides Jessie and James, know who Giovanni is? Not to mention in canon, he doesn't seem to care who Jessie and James are, so it seems unlikely that he would really care who their boss is. (In short, Paul is pretty much a cold character who, while he cares on a level about his own Pokémon, doesn't particularly give a crap about anyone else. So, his role in this and the way he reacts seems a little OOC to me.)
It also seems rather convenient that a portal just happened to be
right there. No looking for it. No need to fight anyone for it or overcome any obstacles to get to it. It just happened to be right where the characters were. Remember that part of what makes a story interesting is whether or not characters have to struggle to get what they need. Don't just make things easy for them, and don't just have them know exactly where to go or what certain things are. Have them work for their happy ending. (This will also allow you to avoid a Gary Stu. Gary Stus are essentially characters whose mere presence in a story causes reality to warp in order to make things go a certain way for them. The classic Stu is a character around whom reality revolves to make things easy. As I've implied just before this long semi-tangent, a story is made more interesting when the character has to put in some work to finish whatever they need to get done. A story that just hands everything to its characters isn't as interesting because there's nothing to watch. We already know how the situation will end as soon as it's mentioned.)
Arceus's voice just talks to him whenever he asks? O_o You do realize that's basically like chatting with or demanding answers from God, right? Even then, it seems rather convenient that all of the answers can just be told to Eric, rather than make him wonder what's going on and try to figure things out for himself.
If you're going to mention any sort of battle, you'll need to describe it. That's because your story, given its nature as a Kingdom Hearts/Pokémon crossover, will probably focus a lot on battling as well as the quest itself. That and it's just not as exciting to say, "It was a long drawn-out battle that Eric won." That doesn't let the reader picture what's going on, so they don't feel as connected to the story. It feels more like they're reading a summary instead of standing right at the edge of the battlefield, watching the action.
Weren't they in a completely different dimension from Pallet Town/the Pokémon world? I mean, they
did just go through a portal, so.
Overall, I'd hate to say it, but this needs a lot of improvement. It was readable, but it feels like you're rushing a lot. As a result, there's a lot of apparent plot holes, and a lot of things feel like they're just given to Eric and the others. Moreover, you don't really give the characters room to develop. You don't let them react like people (or developed characters), and every time you present them with a possibility of trying to figure a problem out for themselves, either the problem resolves itself conveniently (example: instead of trying to search for the portal, it just happened to be right next to them) or a legendary comes and gives them the answer (example: Arceus explaining the Dimensional Scream, Mewtwo explaining how to get to Pallet Town). As a result, it's a little harder for a reader to focus on what you're trying to tell us because we're not given any opportunity to picture what's going on, we're not shown the characters struggling, and we pretty much know that every problem will essentially be solved within a few lines of it being brought up.
However, I will say that it's not bad for a start. You seem to react well to reviewers, which tells me you're eager to learn and keep developing. My advice to you is to sit down and take your time. Plan out details in your story. Describe as much as you can. Avoid summarizing and making things easier for your characters. Even read other fics on this forum or published books to see how they treat description and different problems. You
can get better; it'll just take a bit of hard work to do.
Good luck!