San and her best friend Mayu attend a boarding school for girls on Japan’s Southern Island, but their studies are interrupted when they and the other students are recruited to help the war effort as assistant nurses. Sent to the front lines, the girls must deal with more than just the threat of enemy bombs overhead. Stuck working in the horrifying caves of a field hospital, San wishes she could wrap herself and her friends in a cocoon of protection. But invisible threads of affection are no match for the carnage that surrounds them, and more students perish day by day. Worn down by starvation and loss, what will San and her remaining friends do when they are told to find their way home through the fields of war?