Arpeggio of Blue Steel

"Chihaya Gunzou, captain of the sentient submarine known as I-401, is renowned for his unorthodox tactics. His unpredictability is a strength when it's just him and his crew against the world, but with two massive Fog battleships attacking their home port, Yokosuka, the I-401 has to team up with a human-built submarine to try to take them down--without letting the Fog ships anticipate their next move!"--Back cover.