The "shipgirls" are girls who carry in their bodies the souls of the naval vessels of the past. They are the only ones who can stand up to the "deep-sea dwellers," a group of hostile vessels born from the bottom of the sea, and they are in the battle to protect the people and the sea. However, they were either wounded or killed in the face of the overwhelmingly massive deep-water fleet, and the tide of the war was swinging sharply. In the midst of all this, the destroyer "Shigure" was assigned to a new fleet. The new fleet to which she is assigned is the "First Ranger Unit" and its "Third Unit" (1YB3H). However, the fleet was a "mish-mash" of the old battleships "Yamashiro" and " Fusou," which had been deployed in the rear, and the only other ship, the aircraft cruiser "Mogami," as well as four destroyers. As part of a mission to regain their lives by using all their remaining strength, Shigure and the other 1YB3Hs set sail for the doomed straits on a decoy-like mission to cover the main force.