In the midst of a prolonged battle against the alien BETA, high school student Takeru Shirogane awakens from a haunting dream depicting humanity's downfall. Shockingly, he realizes this nightmare mirrors his existence in an alternate reality where a desperate project, Alternative V, dooms most of mankind. Driven to alter this bleak fate, Takeru enlists at a military base in Yokohama, which curiously doubles as his old school. Here, he persuades the base's vice-commander, Professor Yuuko Kouzuki, to avert Alternative V through the Alternative IV initiative. Tasked with piloting massive humanoid machines called Tactical Surface Fighters (TSF) alongside his peers, Takeru must swiftly master his skills and exploit his foreknowledge within a tight two-month window to prevent impending tragedy.