とある飛空士への誓約

Kiyoaki Sakagami flies for the Akitsu Federation, and his posting puts him aboard the Elyador, an experimental long-range airship crewed jointly by seven cadets from Akitsu and the Centvoldt Empire. Their route crosses the Polydesmian Sea, straight through contested air. When the escort fleet is destroyed, Kiyoaki, his childhood friend and navigator Mio Seira, and the Centvoldt pilot Ilya Kleischmidt have to finish the crossing on their own. This is the fourth series in Koroku Inumura's Toaru Hikuushi line.