...as far as Yamato and rest of the Midway detachment know.

>and implies that Iona did not defect.

And yet, if she didn't defect, why was she found alone? No black-marketeer would have passed up the chance to put multiple Fleet of Fog ships in the inventory.

>
>So, for me, this has three plot holes, and I'm not sure they
>are plot holes rather than To Be Explained Later-s, but here
>they are anyway: first, sans the Arpeggio A-plot it's not clear
>why the Fog developed Mental Models in the first place;
>

Hypothesis: Iona did meet Gunzō Chihaya, but the circumstances were different. Perhaps it was later in the war, perhaps Gunzō met a different member of the Fleet first. Whatever happened, Iona was left alone when the Fleet left, to be recovered by Miss James, and later sold off in Underground. It's possible that if they ever find out what happened to make the Fleet leave, they'll learn something about Gunzō Chihaya as well.

Peter Eng
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Insert humorous comment here.