Twenty years into humanity's war with Vacant, an alien menace that seized control of the orbital elevator in 2079, the tide finally turns. Military forces have developed the Seventh, a cutting-edge mecha fighter capable of pushing the invaders back toward their stronghold. At the Yashima floating base in the Pacific, Miku pilots an experimental black variant of the Seventh alongside her unit, fighting to reclaim the skies and take back what was lost. But Vacant is far from defeated. Each sortie reveals new threats and uncomfortable truths about the nature of the invasion itself. As Miku and her squad execute increasingly dangerous operations, they discover that winning this war may require sacrifices far greater than anyone anticipated. The pressure mounts as command demands results, resources dwindle, and the line between duty and survival blurs with every mission. Vapor Trail burns through high-octane mecha combat while asking harder questions about the cost of prolonged conflict and whether humanity's fight can ever truly be won.