Arpeggio of Blue Steel, Vol. 04

The Fog battleships Haruna and Kirishima have been destroyed through the combined efforts of the I-401 and the Japanese government's "White Whale" sub, and the port of Yokosuka is safe-but the same can't be said for the I-401. While still damaged from the battle, the 401 comes face to face with a Fog sub- marine that lona doesn't recognize, and it's not exactly friendly!

Back on land, Haruna, the mental model of the destroyed ship, is found by Osakabe Makie. The mental model and the precocious human child strike up an unlikely friendship, and Haruna learns that there's far more to Makie than meets the eye.