How, in Kizuna, both Yamato and Taichi know what Sora is up to and even though Taichi and Sora grew apart, they still have a special connection that's here to stay forever and shouldn't be left unsaid
Before you read on, two warnings:
Also, a little note and disclaimer: I can see people percepting this post as a Taiora-shipper heavily vouching for romantic!Taiora and bashing Sorato. Interpret it however you like, but just know that's not how I approached this meta. It's Sorato-friendly and Sorato-appreciative. Sure, it gives reasons for romantic!Taiora to have potential in canon, but it's mostly directed on how I see the -platonic- connection between Taichi and Sora and how it's portrayed in the Kizuna movie.
That being said, I do not own Digimon and therefore this is my view on it. I also didn't read the Kizuna novel, so everything not compliant with the novel is due to that. Anyway, happy readings!
Who remembers the Digimon movie Diaboromon strikes back probably knows how Sora is not present during the fight because she's on the tennis club trip. Or actually on her way back. We learn about this, because Koushiro asks where Sora is and Yamato -being her boyfriend obviously- is the only one who knows the answer. Cute boyfriend, truly!
In the Kizuna movie we see a little call back to this particular scene when Yamato and Taichi are eating together and talk about what all the others are up to (and how they seem to be the only ones who have no clue about their future yet. I feel that, unlike Koushiro I didn't run a freaking tech company at 21??!!! Seriously, who does that?!). Taichi sums up all the 01 Chosen Children + Daisuke, except for two: Takeru and Sora. Of course Yamato knows what Takeru is up to, so Taichi leaves that for Yamato to tell.
As for Sora... I think that's a bit harder and I've been thinking about this since the first time I saw it. Especially after I saw this post floating around on my dash every once in a while (and yes the Taiora-shipper in me wants my Taiora-heart to be soothed BUT this is not the main reason, believe me) and I just think Yamato isn't the only one who knows. Now let me try to explain myself.
The first reaction Taichi gives after Yamato drops the insights on Sora's life is a kind of bored (maybe even a little frustrated?), almost sighing and slightly stretched "Eeehhh" which can be translated to "Yeah...". In the English dub Taichi's 'yeah' sounds even more frustrated and almost... disappointed? Also look at the face above! Taichi doesn't look pleased in my opinion, at all. See it for yourself.
Anyway, when we take all of the above in consideration, we could interpret Taichi's reaction in two different ways:
"Yeah. Ok. Cool. Not interested."
"Yeah. I know. It stings. Thanks for reminding me, dude."
And to be honest, I can't imagine Taichi not being interested in Sora (from a platonic perspective), so I'd go with the second option. Taichi knows that Sora's into Ikebana (and if we believe the one Christmas Tri interview, Taichi also knows about Sora's designer aspirations), but he doesn't include her in his enumeration, because why the heck would he talk about his friend's girlfriend??! Besides, talking about Sora seems a bit more painful to him than talking about the others. A reason for this for example could be that it's pretty painful to see and feel yourself slowly fading away from your oldest friend due to the difference in life paths. Yamato on the other hand starts talking about her, because it's his freaking girlfriend so OF COURSE he wants to talk about her.
This also brings me to the part that Yamato knows that Taichi knows what Sora is up to. After Taichi gives his sighing reaction, Yamato reacts by stating something very painful YAMA MY BOI WHY DO YOU BREAK TAICHI'S HEART LIKE THAT??!!! the obvious no one likes to admit.
"Things can't stay the same forever..."
Look at Taichi's sad and pained face!! The fact that Yamato says this seems to hit something in Taichi, especially after briefly talking about Sora; Taichi's oldest friend... It could even point in the direction of Yamato knowing Taichi and Sora grew apart, as if he wants to make clear to Taichi that it's okay to let go of old friendships as it's part of life (and not because Yamato is afraid to lose Sora to Taichi or whatsoever).
You know, that really pains me. Ugh, this movie will be my death one day... Carry on!
Throughout the rest of the movie, however, we see how Taichi and Sora still maintain some kind of 'connection'. For example how they were silently in pain, waiting for the inevitable, while the rain poured down (I know that's scenography, but it could even be a weird-ass nod to the Our War Game Taiora drama in the English dub...), their scenes following up each other. Also note how both Piyomon (+ Sora) and Agumon stare through the -left panel of the- window... Sad.
~See this edit~
How Yamato is stopped by Takeru, Jyou and Mimi (a.k.a. team Hope) and Taichi only by Hikari and Koushiro. Clearly there's someone missing in team Light and that someone must be Sora on Taichi's side.
And of course the whistle (I still don't get Yamato's dub-line "I used to hate that damn whistle," like, where did that even come from??!! It's stupid) blown by Taichi to which Sora reacts by literally calling out his name with the extra of a hand on the glass, reaching out to him, but unable to help because she's seperated (feels distanced...) from him.
~See this edit~
I even found this little thing you might miss with the blink of an eye. Or maybe I am just an idiot and I only spotted it now and everyone else is like: "Yeah, we already knew, old news." Gonna meta on it anyway
So anyway, in the 'staring to the pouring rain' scene, where Sora tells Piyomon she decided to not take part in the fight anymore (because SAD reasons obviously), we see Sora tracing two raindrops with her finger gliding down the window, becoming one raindrop.
Then, fast forward in the movie to the scene in Koushiro's office before Taichi and Yamato travel to the Digitial World to save the others and find Menoa. Yamato wonders how if they find Menoa and will have to fight her, the Digimon need to digivolve for that fight, which will probably speed up the vanishing of Gabumon and Agumon. Taichi is aware of that, going into some kind of brave sacrifice mode for the sake of the others, and Yamato asks if he's okay with that. And right before Taichi tells Yamato "No, I'm not. But someone's gotta do it!" we see this one raindrop... gliding down the window... seperating into two raindrops..!!! (To all the gif makers; please be my guest...!)
It HAS to mean something, because it's so obvious and it actually ties those two scenes together! It's an 'Aha!'-moment, a moment where the events turn and will probably mean something like 'Our paths cross and became one all those years ago and now is the time for our paths to seperate once again. In order to do so, we have to let go and start growing up'.
But we could also interpret it in a way it says something about the decisions they make and how they differ from each other. One (Sora) chooses for herself not to fight to stall the process of saying goodbye, the other (Taichi) chooses to fight for the sake of others and with that speed up the said process.
This shows us how Sora and Taichi differ from each other, maybe even have grown apart because of that for that matter. But it could also be a hint to their bond and how they still, unknowingly, learn from the other's actions, thoughts and insights in some way. That it's useless to try to avoid the inevitable when it's clearly approaching full force. Because it's fate. At the point the two raindrops come together, both of them don't want to see that fate yet, but when the raindrop splits again, they've come to the conclusion to just take things the way they are (it's the 'Aha!'-moment for all the Chosen really, but it's so typically staged as a Sora vs. Taichi thing, as a symbol for everyone. Take it from someone who works in the theater field and is schooled in theater practices and making choreography. This is exactly how I would like to show my audience their bond in a subtle way without words and how that contradiction symbolizes the decision everyone in the group has to make eventually).
And for all we know, (this is so painful to say...) that one moment that raindrop splits again as Taichi makes his decision... Sora finds her peace with her decision as well... and this could be the exact moment where she loses her partner and becomes the first of the group with that loss........ Of course that's just speculations. But wouldn't it be the best 'strings of fate' trope-story between these two clearly connected childhood best friends?
So yeah, fate will always bring Taichi and Sora together (in canon: platonic. In fanon: could be any kind of relationship you like). And please, don't be ignorant of that! Whether you ship Sorato, Taiora, Taiyama, Taiorato, other Taichi, Sora and/or Yamato ships or none of them at all. These two soccer buddies hold a special bond with each other one could almost call t e l e p a t h i c~... Here's a little Digimon novel reference to that:
Taichi and Sora may have grown apart for now and Yamato is aware of that. But I believe Aang can save the world these two old friends have a connection that will last a lifetime and they will grow closer again over time as they grow up into beautiful adults!
Actually, the Kizuna events will bring the whole group closer together again and that's a headcanon that lives rent free in my mind <3