From The Heretic Knowledge Vault
An airship, first seen (or at least first named) in the run-up to the grand climactic battle in Praenubilus Astu. It is part of the fleet that the Tsuirakuans are sending to the underground city as follow-up to the advance party consisting of Sarine, the Amraphels, Captain Aphel, and so on. Bani Igaaru's duties, as a low-level battlemage, include loading this thing up (with the help of Corporal Matsu and a golem or two) with all the supplies it will need upon arrival.
In a normal universe, that would be about all there is to say about this vessel. However, the Poe-verse is not any old universe. When the Senilisized Meji Hinadori drops by to chat with Bani, and discovers that she's making heavy going of the loading process, she decides (over the objections of commanding officer General Izayoi, who's supervising operations) that she wants to "borrow" the Akizuki to take her to Praenubilus Astu too. A staredown between Meji and the general ends in the former's favor, after Bani gives her a character reference that can reasonably be called "ambiguous." This small issue resolved, Meji just waves a magically high-powered hand, and the supplies simply teleport into place. This, it is fair to say, attracts some attention, and General Izayoi decides that he'd better go along on this outing, as will Bani (not entirely to her liking).
Unfortunately, airships don't travel fast enough to fit Meji's needs. (Senilisated or not, the girl's attention span isn't much to brag about.) Accordingly, she decides to speed up the process by opening up a wormhole in space, through which the Akizuki and its sister ship, the Ikazuchi Maru, disappear with a poit, presumably to re-emerge somewhere in the vicinity of Praenubilus Astu. And there, for the moment, the matter rests.