Alright, brainstorming time!

- I would say I envision one world to be our modern day Earth, as if our characters were living among us with the same political/technological/biological strife. And the other world would be a more vast, not as overly populated fantasy realm with more diverse environments/habitats, maybe a different weather/seasonal pattern?

- In terms of how the worlds connect, I hadn't thought of a reincarnation path. It's possible we could use something like doppelgangers? Or some traits or affinities of main characters are mirrored through those belonging to both worlds? I think if we did want to explore a route of people dying, sort of showing up as another version in the other world, they might have to be supporting cast. At first I just thought a whirlwind of blossoms would be the sort of teleportation link between the worlds. If you're into that, we could consider the idea that the weather or maybe the weather that symbolizes rebirth or awakening could be the link between the worlds. 

I do see the fantasy world more on the verge of an apocalypse. As you mentioned, I do see the scale/duality of both worlds. While one (the modern world) is doing well with so many advances, the opposite world would be struggling to just farm and make ends meet. I would say the magic itself would be tied to one world, but if it bleeds into the modern world once things shift, that would be pretty interesting. What if the magic itself was causing the strife in the fantasy world? Maybe it bleeds one world dry and hinders progress, by starting wars, damaging soil, causing disease, etc. Maybe the modern world found a way to filter the magic and force the majority of it to localize and stay within the fantasy world?

- You bring up a good point as to how the native characters handle the transition from one world to the other. 

Since we are using magic (whether or not it's a positive or negative entity...) we could use it as a trope and say it allows someone to easily acclimate themselves in terms of language and maybe outward attire? If we did want to go a step further and ass classes like elves or ones we make up, we could, that would be an interesting dynamic. But it could also add complications where they're not needed.

I do think the changes should be minor in terms of aesthetic but if they took on a more different identity, it would be interesting to see how two people from the same world might change once in the other, and if they'd even be aware of who their friend looks like now (say if separated). 

- In terms of the idea of the ultimate goal and who is working for and against it, I do think it would be easier to first know the true evil or at least, the truth behind the world's connection. Who knows about it in each world? How long have the cycles of prosperity/struggle been happening? Say for example, we do use magic as a negative and evil thing (sort of like a tangible infection) then I would suppose the fantasy world would have a great desire to open whatever gate/border/door between the worlds that is keeping the magic from spreading evenly between both worlds. But do we want the modern world to be outright evil or aware of their deceit?

It also depends on our cast, I do think the more varied the goals and awareness, the more compelling the dynamics and conflicts will be.

Maybe there's some kind of hidden agenda in the fantasy world where someone is aware of why there's so much despair and have something to gain from keeping the world stuck in such a state? Is there some secret society or group that is already aware of the balance between two worlds and has yet been able to find a way to restore things to a more fair situation? Do both worlds have such an organization where they cross paths with the heroes who are out of the loop? Would there be double agents if we went in such a route?

- Now in terms of bringing forth elements of cuteness and wonder, I would say the characters themselves would be the best means to deliver a light, charming aspect to something that is so layered and serious. The need to explore and to solve many people's issues (in both worlds) while reassuring the public that things are changing for the better of both worlds, are things I see happening. There's also the idea of traveling to dynamic places with lots of richness and color. Even if one world is bleak, there may still be places that have been able to stave off such depression. Or in the modern world, there could be hidden places that are rich in magic and fantasy that go otherwise unseen by most.

Or we could also flip things inside out and have the modern world be suffocated by 'magic' where the fantasy realm is bountiful?

- And the protagonists themselves...let's see. I did see them as ordinary but you are right in them probably needing to be special in some way. There is the cliche 'Chosen' route where they end up needing to die/kill someone they've grown fond of in the end? Or we could go the route of a prophecy claiming certain people from opposing worlds would save both of them and restore order? Or we could have some kind of bloodline tied to it where one protagonist is related to a future antagonist and ends up having to rally some resistance against their friend?

Again, the dynamic and tones will depend on our characters and what sort of personalities and goals they have.

So now I might like to pose some questions to you since I feel like I'm not contributing enough so here it goes!

- How are you with visual aids? I have a stockpile of anime scenery and location pictures which I do think could enhance the story as we move along. I also find them pretty inspiring. 

- Now cast sizes! I see us using 2-3 characters each, but we'd be focused on our main character. I do see side characters coming and going and we'd be able to share them as needed. Since this is such an ambitious idea, I don't want either of us to end up feeling burnt out or tired or bored or overwhelmed or anything like that. So I'd like us to be encouraged to swap out NPCs for main roles every now and then to shake things up. Maybe a priest who's often been in the background now wants to see more of the world and help the cause and maybe an antagonist's best friend is injured and needs to recover so that's how one of us could swap a major role. What do you think?

- That sort of leads me into my next point. If we do want to take on more roles, I would insist our posts not get too out of hand. I've had this happen with great stories in the past that then fizzled out because both me and my partner felt too daunted at times. So I would be okay with giving a main character 2-3 paragraphs while lending any of the other 1-2 sides with just 1-2 paragraphs. As much I like writing a lot, it can be a little tiring. Now I can certainly give 4-5 paragraphs per role and while it is fun, it's not something I necessarily [i]want[/i] to do if there's already so much going on, you? 

- Lastly (for now, I need to go write an outline for my next essay), I think it would be fun to have the story take place between both worlds so the 'two world' thing isn't just some plot device. I want us to care about both worlds and people in both worlds. Whenever I start one of these, we never get to the point where our characters go back to where they came from, even for just a few days. I'd really like to juggle lives in both worlds because how often is someone going to vanish for a week or two without having said something? If two people do vanish from our world, I would expect there to be some reaction or consequence. I just don't want characters to find a new world and forget the life they still have in the other world, you know?