Following the successful repulsion of Aftokrator's invasion, the Border Defense Agency readies an away mission into the Neighbor's dimension. However, as with prior scouting expeditions, only A-rank teams are guaranteed a place. As the B-rank wars persist, Osamu Mikumo and the rest of Tamakoma-2 swiftly battle their way to the top, aiming to secure a promotion before the operation commences. Meanwhile, a new Neighbor vessel approaches Border Headquarters. Observing that the attackers are targeting the Border Expedition Ship, forces are hastily dispatched to engage them. However, with fewer squads available due to the ongoing rank wars, the organization falls into disarray. This latest offensive by the Neighbors leaves the fate of the crucial expedition ship shrouded in uncertainty.