Okay, here's how I think the probabilities break down:
- X%: Asuma hears about it and pays attention.
- A%: Asuma thinks it's the result of a Leaf experiment. He narrows the culprits down to the usual suspects, with us up there on the list (with, say, the Nara, Oro...). That happens even if we supply no additional information.
- Q%: He calls said usual suspects up and chews them out for unauthorized/unwarned WMD tests. This leaks the information of the nuke to everyone else Asuma suspects, since they all receive "if this was you, warn me the next time" letters.
- (A-Q)%: He decides to let it slide.
- B%: Asuma thinks it's enemy action. He calls up the Clan Council. Picture this scene in detail: we receive a summon, show up, he's furious like he'd been at the start of the war with Rock, he immediately issues orders to break peace. What do we do? We can let him do that, then approach him post-factum/send the letter I proposed. He'll then have to reverse his orders. Not only would we force him to make a fool of himself, this sequence of events would likewise let everyone else in Leaf make the inference that it was a Leaf WMD deployment (while otherwise this information may have been limited to just the Tower/Asuma).
- (X-A-B)%: Asuma thinks it's neither of the above (that it's a freak weather phenomenon, chakra beast weirdness, etc.). In this case, he still likely calls up the Clan Council and starts a massive panic (a chakra beast/weather phenomenon that can randomly do that is less spooky than "enemy action", but still spooky), but in this case we can just watch on. It'll be a waste of Leaf resources, but at least not an AMITY breakdown.
- (100-X)%: Asuma doesn't hear about it/dismisses it if he does.
We want to make B be near-zero. But its probability mass has to move
somewhere, and that can only be one of the other possibilities on this list (unless you think this list is non-exhaustive, in which case: what are these additional possibilities you think of?). Let's consider our options, then:
Whether it's Scenario 1 or Scenario 2 (Asuma hears vs. doesn't) seems heavily predetermined. We don't
know the value of X, but I expect it's either ~0 or ~1: either it's totally the sort of event that'd absolutely be noticed by Asuma, or it's totally
not — we have no a-priori reason to think it's
just on the cusp of notability. In other words, we can't
subtly shift the probability mass from Scenario 1 to Scenario 2: if X% is ~1, we'd need to
massively compromise Leaf's ability to collect intel, to force the world down Scenario 2.
Similarly, I don't immediately see how we can subtly hint at Scenario 1.3 (natural phenomenon/other) such that it's heavily prioritized over Scenario 1.2 (if counterfactually it wouldn't). Let alone do so in a way that doesn't reveal us for a liar if we ever
do tell him about the nuke, down the line.
Which means we have to shift Scenario 1.2's probability mass to Scenario 1.1: we need to take some actions such that, if we're in the world where Asuma certainly hears about this, he's sure to assume it's been caused by a Leaf ninja, and preferably accidentally (to drive Q down as well). And
the letter scheme I'd proposed does just that. Crucially, it doesn't any leak information that Asuma wouldn't have inferred in Scenario 1.1
anyway.
Now, of course, if we're in Scenario 2 (X is near-zero, Asuma is unlikely to hear), the letter would shift us to Scenario 1, and that's undesirable. The question, thus, is: what is the actual value of X? Are we in the world where Asuma is certain to hear about this (and therefore we should send the letter), or we're in the world where he certainly won't, or won't care if he hears (and therefore we shouldn't send the letter)?
This is where I'd wash my hands of the issue and leave it up to Mari.
Fake edit: Hm, I suppose we
can instead pretend it's a seal-failure result of bijuu notes research? That may be what Asuma thinks in Scenario 1.1 by default, and in that case the elaborate anonymous-letter scheme would shift probabilities
away from "an accident" (since we'd have no reason not to come forward with the "real" explanation, and the failure to do so would reveal we have somethin' to hide). But we'd have to lie-by-letter about it as well, and it
would be an explicit lie.
