Arpeggio of Blue Steel Vol 8

Arpeggio of Blue Steel Vol 8 by Ark Performance. An Action manga rated Teen, published in English by Seven Seas in 2010.

Humanity has lost control of the oceans to the Fleet of Fog, a mysterious armada of warships with advanced technology. Young captain Gunzo Chihaya teams up with Iona, the humanlike avatar of a Fog submarine who has defected to humanity's side. A naval sci-fi action series.