The [[submarine]] [[I-401 (submarine)|]] as depicted in [i][[Aoki Hagane no Arpeggio]][/i]. It is the organization Blue Steel's flagship.

While the other members of the Fleet of Fog generally lend their names to their Mental Models (i.e. [[personification]]s), the I-401's own Mental Model has a separate moniker for herself, [[Iona (aoki hagane no arpeggio)|]], which the people within Blue Steel and its circle also use. This is why the I-401 and Iona have separate tags in Danbooru.
i-401 (aoki hagane no arpeggio)