Sheena lives in a remote orphanage where girls without families are raised as weapons and drilled to kill without flinching. Unlike the others, she quietly hopes the war they are bred for will end. The night her roommate dies, Sheena runs into a blood-soaked girl who turns up the next day as a new classmate named Mimi, smiling at everything the place does. The two grow close inside an institution built to make that impossible.