Humanity is struggling to survive after an apocalypse, contending with Filth Monsters, also known as Limbeekoon. Massive mobile cities, known as Regios, provide sanctuary while powerful weapons called Dite, which utilize Kei energy, enable them to fight off the dangerous monsters. Layfon Alseif seeks to start anew at Zuellni Academy City and forget his tumultuous past. Unfortunately, Karian Loss, the cunning Student Council President, and Nina Antalk, the Captain of the 17th Military Arts Platoon, who recognizes his incredible abilities, confront him with his dark history. Nina offers him a place on her team, but Layfon's unique powers and hidden past may prevent him from accepting the offer.