After her request to start up a chess club at her high school is shot down, 3rd-year Mimoko Inoue unexpectedly finds herself face-to-face with a member of the Desperado league, an infamous underground chess league. The Desperado attempts to kidnap her, but is stopped by Okisato Tanabe, a seemingly ordinary 2nd-year student from Mimoko's high school, who wished to join the chess club. However, the Desperado then brings forth his DESPER, a mysterious device capable of forcing people into Chess matches where anything from cash to lives can be wagered, and forces Okisato into a death match with him while Mimoko is forced to watch. Will Okisato be able to get out of this mess, or is it checkmate?