This is just a brief overview of the general setting in Q&A format, given that I'd rather not drop expodumps left and right but contains information which is useful, but not necessary to know. If you have more question, just leave 'em in the comments or reviews. The questions are mostly serious, except for the jokes at the end. (Don't worry, I haven't gotten harassed that badly online … yet.) And, should you somehow get all the references I've made, kudos!
Q: Do I need to have played both Fire Emblem and Persona to read this?
A: My advice is as follows: at least one of the two is preferable, it's best if you have some familiarity with the Persona universe and 3H's story.
Q: Is this set in the Persona universe, and when is it set if it is?
A: Yes, this is set in the Persona universe, and as for the year – let's call it around 2018(ish), but 20XX works just as well. I would say 2020 but … well, you know why I'd choose to avoid setting it in this year. It's somewhere in America, probably on the west coast. That seems about right.
Q: Are the backstories for the characters still basically the same?
A: No! Half the backstories don't even work, like the true nature of Nabateans, the function of the Crests, the truth behind the Duscur Massacre, and Jeralt's true age, among other things. Nabateans work differently, Crests work differently, and Jeralt is actually as old as he looks. Among other things. Obviously, changes to certain character's backstories will have to remain a secret for the time being, given that part of the plot is the main characters discovering the truth.
Q: Will [insert Persona character] show up in this story?
A: Igor, as the host of the Velvet Room will show up. Everyone else, unlikely, given that this is set in America. There might be an easter egg shown off somewhere, like I'll probably have Hilda watching Neo Featherman in the background at some point.
Q: What Persona is this based off of?
A: Well it has the general theme of 4, but I'm using a lot (but not all) of mechanics found in P5, and my favorite one is Persona 3, so … I don't know? Let's say it's based off the franchise in general. Its not going to be exactly like any one particular game.
Q: Oh. That's fine. So you're going with the traditional spread of the Personas and elements, right?
A: Most of the Personas that Byleth will use will be from the main game, though I might grab some legends or myths I'm fond of that hasn't shown up in the main series. The elements are different than any individual game, but based off several games.
Q: What are the elements?
A: There's slashing and piercing for physical; wind, fire, ice, electricity, and nuclear for magic; plus light and dark for (mostly) instant KO spells and almighty for … well, almighty. Psi is getting removed because, honestly, it's really just too many elements. I get the concept of having every character have a unique element, but it served P3 and P4 just fine to have characters with overlaps.
Q: If you die in the game shadow world, do you die in real life?
A: Yes, but instant KO spells are just knockouts when used against the party, as per the way the game functions. The characters will not die instantly from getting hit with a Mudoon spell. Remember, this is half Fire Emblem, and enemies do not have access to insta-kills in Fire Emblem.
Q: Byleth is 21 in-game, not 25.
A: I'd like a slightly larger age gap if he's supposed to be a teacher, especially given that the average age of the cast has been raised to college level, though I'll try to avoid giving specific ages to the cast where possible.
Q: Speaking of, why is it set in a college? That's older than the students in-game and Persona is traditionally in a high school.
A: It makes for sense for the vastly diverse cast to be at a college together, rather than a high school which is usually local students. Also, Garreg Mach is the equivalent of a college in 3H, just they did everything a bit younger back then.
Q: Is the roster just Golden Deer?
A: I'm going with a mixed class approach so there will be characters from all the classes. Only a handful of Golden Deer students will be part of the team.
Q: Have the roster and Personas of everyone been decided? And if not, can I give suggestions?
A: Yes to the roster, no to the Personas. Some final Personas have yet to be decided. You can give suggestions, but you might be suggesting something that I've already decided on. Even still, if it's a good suggestion I'll at least listen to it.
Q: Will every Three Houses character have their own social link?
A: No. That's an absurd amount of writing. I'm just one person, and I'd like to have a reasonable prospect of finishing this, you know.
Q: But there will be social links?
A: Yes, but not in the way the game does it with levels 1-10. That's fine for a game, especially since Persona games tend to have massive amounts of downtime between new areas getting unlocked, but, again, that's an absurd amount of writing. Social links will advance in much larger increments, and for the most part, provide bonuses like they do in P5.
Q: How many Arcana are there going to be?
A: Just the normal deck, no plans for a Jester, Hunger, Faith, or Aeon, I'm afraid. Twenty social links is already a lot of social links. Those have all been decided too. At least, that's my current plan, which is, naturally, subject to change.
Q: Will [insert character here] be one of the Social Links?
A: You can't honestly expect me to answer that. But make no mistake, every character in 3H will show up at some point. Just perhaps not contribute to the plot in a meaningful way.
Q: Why is it Golden Deer? I wanted [insert route here]!
A: Claude fits the narrative structure the best, as this is essentially a mystery and Claude has the most focus on discovering secrets. Edelgard and Dmitri will still be important to the plot, though. Don't worry.
Q: But what about Ashen Wolves?
A: What about them?
Q: Are you going to put them in?
A: They aren't going to be any of Byleth's Social Links, if that's what you're wondering. Again, see the absurd amount of characters that I'm already going to be dealing with and the fact that they have an awkward place in cannon as it is. I'd like to, but it's just not in the cards. That said, I'm sure I can squeeze them in somehow to show up for cameos.
Q: Can I write spin-offs detailing characters that you aren't paying attention to in this universe?
A: That sounds less like something someone would ask and more wishful thinking on my part, but sure. I don't mind someone writing omakes or even using a lot of my concepts to write an alternate path. This is fanfiction, for goodness sake. I can't complain about you using characters that I'm stealing from somewhere else.
Q: Will Byleth romance [insert character here]?
A: I'm not averse to pairing Byleth up with someone, but the pool is smaller than you think. There will be no student-teacher romance on my watch, thank you. Also, don't expect it to be integral to the plot.
Q: Was that a dig against romance in 3H?
A: No, it was a dig against P5. 3H at least has the decency to save romance until after the time skip.
Q: What are your cannon pairings for the Persona games?
A: I really don't see how that's relevant to the story, but if it is, they'll show up when they show up. Don't expect them to be groundbreaking, though.
Q: Your knowledge of Persona and l33t pro strats suck. Byleth should be using [insert Persona here] with [insert skills here] against [insert foe here]!
A: Yes, I suck at Persona. Please stop making fun of me.
Q: Do you need to go on a lengthy explanation of the historical context of everyone's Persona?
A: It's very important to the plot, I assure you.
Q: So I read your previous fanfic and I realized that at a certain point Robin just becomes Dimitri. Do you feel bad for shamelessly ripping off of Three Houses?
A: I feel like this is starting to become harassment for some of my life choices.
Q: You probably also think you're pretty clever making the self-insert character a writing teacher? Is that what they call 'write what you know'?
A: Please stop.
Q: Persona 3 sucks. Why would you call it your favorite Persona game?
A: What have I done to you that you would attack my opinions this way?
Q: Does Roy appear in this game?
A: Oh, for [CENSORED]'s sake.