The central conceit (borrowed from a Japanese anime) is this: before reaching puberty, young girls discover that each contains the soul of a warship of the Imperial navy. With training, they learn to don the armor, guns and aircraft of their titular ship and so become that ship. Enrolled in the naval academy, the Fleet Girls are molded into an elite force pledged to defend the emperor at any cost. In other ways, they’re just like high school girls anywhere. Morale is high until one day, northeast of Midway Island, things go terribly wrong. When asked to make the ultimate sacrifice, the young women must assess the value of their civilian lives in practical terms.