Nagisa, a high school student stripped of her memory and separated from her partner during a covert mission, finds herself demoted from elite Special A status to the lowest-ranked E Class, a dumping ground for troublemakers deemed incapable of forming meaningful partnerships. To help her select a new Buddy from among these misfit peers, the school arranges a camping excursion—an outing that takes an unexpected and dangerous turn when crisis strikes in the wilderness.