As much as I love Ohtani and want this all to be someone else's fault, I'm really leaning toward "B". I would be thrilled to be proven wrong, but none of us really knows anything yet. We're all just speculating.
FWIW, IMO the most salient "facts" (from the affidavit) that go towards Ohtani's innocence/non-involvement would be:
-Gambling winnings go to Mizuhara's account, not back to Ohtani's.
-Payments for losses come out of Ohtani's account.
-Mizuhara purchased baseball cards for himself with money out of Ohtani's account.
-Mizuhara impersonated Ohtani to clear wires at the bank.
Others are potentially huge, but not really nailed down in the aff:
-Ohtani's non-access of the account.
Many others are more neutral/unknown. For example, Mizuhara apparently used Signal to communicate with the Bookie, so had some idea of communication discipline. If so, non-texting with Ohtani isn't really that probative. Likewise, the idea that Mizuhara had gambled before only gains weight if it was unusual, while the Aff is silent as to Ohtani's prior gambling (if any.)
Overall, the aff paints a picture of Ohtani being comprehensively duped. Is it a complete picture? No. Is this partial picture a likely picture? Well, perhaps not
very likely, but as I said, Mizuhara running rings around everyone would absolutely not be the weirdest/stupidest thing I have seen - by a longshot.
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However, as a somewhat separate matter from our social judgements, there's absolutely enough gray space here for any non-brain-dead defense attorney to tell Mizuhara not to plead guilty until some questions are answered. Maybe Mizuhara has counsel - maybe he does not. Maybe those questions have already been answered to his counsel's satisfaction. Maybe the deal is fantastically good. (We just don't know yet.)
When looking at things in this bucket, you have to keep in mind the prosecution has to prove the case beyond a reasonable doubt. So this might be a situation where there's enough evidence to convince a jury that
it's way more likely than not, that Mizuhara did this all on his own, but not enough to criminally convict him. Or to say it another way,
something showing that Ohtani knew, or possibly knew, would be significant. Even if that
something wouldn't be enough on its own to make a case against Ohtani himself.
That's more of a background/precautionary thought on my part, since it looks like Mizuhara is going to plead guilty.
But if he changes his plea, I don't think anybody's current opinion needs to wildly change.