Arpeggio of Blue Steel

After humanity lost much of its land due to rising sea levels caused by global warming, the Fleet of Fog established dominion over the high seas.

Now the captain of I-401, Gunzou sets course for Yokosuka after accepting a mission from the Japanese government.

Yokosuka is now under attack by the fast battleships Kirishima and Haruna; I-401 sets sail to intercept them within the defensive barrier.

Defeated by I-401, Haruna has managed to retain her mental model form, but only Kirishima's union core has survived.

Iwo Jima has been surrounded by the Fleet of Fog; Gunzou invites the mental model Kongou to the island to speak with her.

The Mental Models work together to withstand the attack on Iwo Jima from the Fog's East Patrol Fleet One.