Yuri leaves initially because he was chasing after the aque core blastia thief pretending to be Rita, and this more or less leads him to help Estelle out, whose shelterness left her very desperate for aid and was very lucky that the one man she asked for help was related to Flynn (and her telling this to Yuri adds another reason for Yuri to go out into the world to ensure Flynn is safe, even though he denies it at times). This little wish leads to Yuri's dislike for the empire uncover a much darker plot that he tries to keep Flynn away from and enjoying Estelle's company, and Estelle learning that her shelterness had a very ulterior motive that ended up taking the curious Rita for the ride because Estelle can use artes without needing the bodhi blastia she carries around for show and Rita wished to learn why that was like that.
Karol is pretty much the utility member because of his indirect knowledge he got from all the guilds that threw him out. The whole journey is his personal character growth, though it doesn't do much for the story itself other than one act of badassery.
Judith tags along because of Estelle's secret putting the world in peril and confusing her when Ba'ul was drawn to her instead of the Hermes Blastia that Judith has been destroying around as the Dragon Freak, which makes her wonder if she should continue doing what she's been tasked to do by higher powers and in the way helps her grow in her hasty decisions without telling the group.
Raven has a HELL number of reasons to be with the group that I wouldn't be able to summarize because he happened to have a lot going for that got much more expanded in the Empty Mask manga.
Repede is the team pet but that's it.
Patty is sadly the one without much because she herself recovers from her amnesia halfway through the story but purposely puts her issues for another time because the group is too busy saving the world to mind her issues until she has to confront them near the end and she's mostly there for cutscenes to add a little more of flavor. Despite the fact she has ties with the big bad, Alexei doesn't even acknowledge her presence at all.
Flynn, well, the poor guy suffered oh-so much because Yuri wasn't around to reel him in, just as Yuri suffered from not having Flynn around during his darkest moments.
I wouldn't say the characters are hollow other than Repede and maybe Karol and Patty.
...The real problem is Part 3, though. It basically becomes the Estelle & Rita Show because those two are the ones doing the hard work, with some Yuri, Karol, and Patty bits by the base.
I just mean, as far as the characters joining the journey, I think most of them are plot-shaped contrivances. In Yuri's case, he's dissatisfied with the empire and how the lower quarter is treated, but he's still been farting around there for years, and at the first opportunity to leave, he's willing to chase a thief halfway around the world. It just seems like a such a slight impetus, and if that were really all it took, he shoulda been gone years ago. In Estelle's case, she's worried about Flynn, yes, but why does she have to chase him across creation just to tell him in person? Not to mention that subplot barely goes anywhere. Karol's issue, I think, is that he just sort of sticks to the group without any particular reason, even before he's fired from the Hunting Blades. I like his arc overall, but it is kind of high concept, where most of his motivation comes from the intrinsic idea that guilds are good, and he needs to be in one. I think my issue with Rita is that she doesn't give any reason why she wants to come with the group. She noticed that about Estelle, yes, but she kind of just unilaterally declares that she's going with them, even though Yuri still isn't fully convinced she's not the thief. Raven has multiple reasons to stick with them, of course. But the issue is that they LET him, even though they're openly displeased and/or distrustful. (Admittedly, I don't know what the Empty Mask manga is, either.) I still think Judith is flimsy -- though she'll say much later that she noticed that about Estelle in Heliord, it's not like she approached the group before she met Yuri face-to-face, so it's still not apparent to me why she didn't just continue doing what she was doing instead. Heck, the group basically nabs her when they're fleeing Dahngrest, even though they barely know her.
I do think a lot of this goes away in act 2, when they form the guild, but it just seems to me like they had trouble actually getting to that point. Kinda goes hand-in-hand with the common complaint of the first section of the game feeling like an extremely drawn-out prologue. Still, I think it feels a lot like they're just forcing each member into the party ASAP, and figuring out their role later. It's commonplace in older JRPGs for sure, and born out of practicality (like I said, it WAS pretty annoying to have Patty pop in and out several times), but it's noticeable, and something I think most stories try to avoid if they can.
And I like Repede. I feel like a lot of games, and especially the more recent Tales, err on the side of having a smaller cast so that they can give each member a more fleshed-out story. Repede ducks out of needing a big story arc because he's a dog, but gameplay-wise, he fills a pretty unique niche, and is different to play as. So, he lets you have more characters and diversifies the gameplay, without the need for the creators to develop and integrate a whole new character into the story.
Too bad only Europe gets the special Hootle version of Arise.
I wonder if it's $200 there, too? I've bought the last few special editions, but I had to pass on this one. Presumably, so did a lot of other people, because it looks like it's still available to pre-order.