Earth is under constant threat from Neighbors, invincible monsters from another dimension that destroy our way of life. At least we have the elite warriors of Border, who co-opt alien technology to fight back! Meet agent Osamu Mikumo, not the best, but along with his Neighbor friend Yuma, he'll do whatever it takes to defend life on Earth as we know it.

The exam to determine who gets to be on the away team begins, and the challenges facing Tamakoma-2 and the other squads selected to participate are piling up fast! All of the squads are split up into new teams and assigned captains of varying skill and experience. The teams are then sent to live aboard a simulated away-mission ship where they must complete a series of individual and group tests. With Tamakoma-2 split up, Osamu loses the support of his stronger and more skilled squad members and must cooperate with people he only knows from fighting in the Rank Wars. And his new teammate Katori, despite her talent for battle, is difficult to work with and already hates his guts!