Three stories set after the "Kageri Saku Senkō" event of the Senki Zesshou Symphogear XD Unilimited smartphone game, in which Miku travels to a parallel world and helps its version of Hibiki, referred to as "Grey Bikki" or "Edge Bikki", who didn't have her version of Miku to mentally support her following the Zweiwing incident, in order to save her own Hibiki, whose soul was linked with Grey Bikki.