In a post-apocalyptic world dominated by mutant animals known as Limbeekoon or Filth Monsters, mankind is forced to dwell in gigantic mobile cities known as Regios and learn to utilize unique weapons known as Dite to fight themselves by harnessing the power of Kei. Layfon Alseif is hoping to start a new life and forget his past in the Academy City of Zuellni. His history, however, has piqued the interest of Karian Loss, the manipulative Student Council President, and Nina Antalk, a Military Arts student and Captain of the 17th Military Arts Platoon, who recognizes his potential and determines he's the ideal candidate to join her squad. However, with a secret background that won't let him go and unknown powers beyond normal, Layfon might not be able to handle it.