#i think this counts...

I like to think that he comes into being the instant Shinichi commits to the lie. 

As soon as he cooks up the name Conan Edogawa and deceives Ran about his identity, they split - if only because the act of assigning himself a pseudonym for the reasons he does effectively commits him to consciously sequestering his “real” self from every part of his new life going forward.  Conan must now be introduced as an entirely separate person henceforth and, whether he intends to or not, this starts giving his creation legs to stand on... but it’s innocuous at this point.  There is no active hatred of this other self (although you could argue there is, at the very least, a passive dislike) and so Shinichi-- let alone Conan himself-- isn’t even aware that he’s there.  They cooperate together as a single entity, thinking the same thoughts, acting on the same instincts, etc. etc. etc.

Since Conan’s existence is reliant on Shinichi-- from the scale of the lie surrounding “Conan Edogawa” to the way he thinks about him-- he only starts to really emerge the longer the bit goes on.  Another day goes by and Shinichi perpetuates the lie to yet another person, hates himself just a little more for it.  Maybe some days he has to lie a lot, has to make up an additional story or another fake person to supplement it, and then he despises that people remember the lie-- that it was Conan who's marked these people’s lives rather than his true self, Shinichi Kudo.  Each day adds another fleck to Conan’s impending self-awareness, even on days where Shinichi tells no lies - because not telling the truth is still lying.

I like to headcanon the (noticeable) start of the split in Coffee Shop Murder Case:

(Definitely not because of the way Shinichi is portrayed as completely separate from Conan during Shenanigans... definitely not.  I’m pretty sure even the JP dub for this one has Shinichi-- rather than Conan-- speaking for his own thoughts a few times, the thing that's the norm for the Funi dub??  Hello????)

His behavior is obviously being driven by a combination of jealousy and denial for romcom laughs, but he also really fantasizes about mauling a complete stranger, which... well... 

Not that I think he doesn’t already tend towards violence or anything sksksk (Episode 1)

As early as the first episode Shinichi is already established to be both reckless and... at least a little violent, to put it mildly (frankly, I think he’s more desensitized than anything, and so his threshold for acceptable violence is completely fucked), which really just lends itself to the slow-burn-nature of this AU.

(In this AU, canon proceeds pretty normally up until around... ehh... The Desperate Revival? with small, off-kilter details here and there being the only indication up until then that something is... awry.  From there, canon returns back to normal but the divergence is on the uptick... something weird happens in one episode that maybe gets dismissed as a fluke... then it comes back twofold in the next and stays... wash, rinse, repeat... until the whole thing eventually forks off into its own canon.)

I guess what I’m getting at is that Conan’s emergence starts as the barely-perceptible, merely more frequent tendency towards brutality or impatience or any number of negative traits which Shinichi usually has a handle on, and that I interpret whatever rascal behavior he exhibits going forward as just that: the slow reveal of Conan.  Shinichi doesn’t notice when it starts happening (nor would he be able to) because it’s so gradual and creeping: maybe a violent thought here, an angry thought there... They should be punished, he thinks one afternoon on a case.  They deserve to be punished, he thinks on another.

An outsider looking in-- if they even notice-- would likely dismiss the shift in demeanor as coming-of-age behavior.  And even if they don’t, whatever it is is hardly insidious, just as the sometimes-entertained thought that Conan and Shinichi could be one and the same in the first place is absurd.  “Does Conan seem different to you, lately?”  No, no, he’s merely growing up, they’ll say.

Why is Conan so violent?  Why would he be so hateful, why is that the indicator of his presence above all else?  It’s not necessarily the only indicator, but he is the receptacle for all of Shinichi’s lying, all the unspoken-- but apparent-- self-loathing for feeling like he has to lie in the first place, and when the base personality is already proven to be prideful and somewhat zealous...

So just as Shinichi’s lying continues unbroken, so do these these bouts of uncharacteristic behaviors.  Little by little they become more frequent, more severe, more strange, and by the time Shinichi inevitably notices something’s wrong, Conan is already entirely self-aware... though not necessarily evil.  There is no defined moment when it happens, no specific point where you can draw a line in the sand and declare that this is when Shinichi was still fully in control, and this is where Conan starts to take the wheel.  Shinichi has a hard time really knowing whether he’s still calling the shots or if he’s just a passenger in his own body.  Is the sound of his own voice only in his head?  He doesn’t remember doing those things...  Is he still even making any decisions?  ...To which the answer is yes; Conan is separate, but still cooperative in the way a younger sibling looks up to and listens to his big brother, but switching between them is such a seamless, effortless process that the resulting ambiguity only hastens Shinichi’s habit of othering Conan as something lesser, something to be hated.

And indeed, Conan eventually swinging towards evil intentions is entirely fed by and triggered by the progression of passive dislike into active hatred.  Time keeps ticking and so far Shinichi has told no further truths, so Conan-- the lie-- is still technically gaining power (and this is why his abilities are technically limitless - the lie becomes so big that no-one really knows how deep it goes).  By the time he “takes over,” he’s already fairly well-anchored in the real world, and Shinichi knows-- at least on a subconscious level-- that he’s marked too many lives, good and bad, for there to be any easy way back... so on top of believing him to be an “inferior” version of himself, he’s also being replaced by said “inferior” version.  People aren’t necessarily remembering Conan in place of Shinichi (the Detective Boys, for example), but as the fabricator of the lie, in his mind... being forgotten is the same.  Nobody can know they are two people, but they’re also no longer a single person, either - how can he not project his grief onto Conan, who has committed the great sin of existing? 

This gets especially bad during the few times he transforms back into his adult self.  These are the only instances (prior to the physical split) in which Conan is definitively caged in the back seat, and so under the spell of some false sense of security Shinichi has a tendency to cast away his inhibitions and tell him how he really feels, so to speak.  Conan is not unaware that he is disliked by his maker, but as the part of Shinichi which wants to impress is also present in Conan... he extends the olive branch at just about every turn anyway, regardless of the sustained animosity between them, the worst of which manifest in dreams.

The nightmares-- which are shared-- escalate alongside their increasingly strained relationship.  Shinichi dreams of losing loved ones-- specifically Ran-- to the Other Him... Conan dreams that he will disappear suddenly, and forget the joy of living... Shinichi dreams that Conan will grow into his identity (a la OVA 9)... and Conan dreams that Shinichi was right all along and that he will be revealed as a monster, which finally breaks him.  “Enough,” he seethes.  “If it’s a monster you want, it’s a monster you’ll get.”

There’s no reason for me to put this here, I just really like this vibe and it’s appropriate skdjfskjdf (Movie 4)

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