Japanese schoolgirl Sakura has her idyllic small-town life turned inside-out when the local men start savagely killing the women. Armed with only her kyudo bow for protection and an English textbook for comfort, Sakura journeys through an apocalyptic world of mayhem.

In a small town with a big red bridge, a run-down apartment, which everyone calls a haunted house, stands still. A few days before the summer break begins, two high school girls, Kaede and Azusa, find a boy living in the abandoned place by himself. Naming him "Mon", they take care of him without being noticed by anyone.