Something terrible happened on Kamioki Island five years ago. Something so terrifying that it erased all recollection from Mari Wakatake's mind while killing every other human on the island! Mari is now enrolled against her choice in a remote girl's academy, unconscious that concealed eyes are watching her, waiting for her memories to return. The most terrible truth of all is buried in her psyche: while Mari was the sole human who survived, she may not have been the only survivor! Mari's last hope may be a strange girl to whom she is oddly drawn but cannot trust when something in a feminine skin invades Kaihou Academy.