Aliens called Savages descend on Earth, and humanity's only defense is the Hundred, a sleek weapon system that transforms its wielders into superhuman combatants. Hayato Kisaragi earns admission to Little Garden, a prestigious military academy floating on the ocean, hoping to become a Slayer and fight back against the invasion. His first day takes a sharp turn when Emil Crossford, assigned as his roommate, greets him with unsettling familiarity, insisting they've met before. Hayato has no memory of her, but something about Emil feels genuine beneath her bubbly exterior. Before he can process the confusion, the school's reigning powerhouse, Claire Harvey, challenges him to a duel. Winning would earn respect and status among the student body. Losing could cost him everything. As Hayato navigates combat training, competitive duels, and the mystery of Emil's connection to him, he discovers that his own past might hold the key to understanding the Savage threat itself. What follows is equal parts high-octane mecha action and interpersonal drama wrapped in a sci-fi military setting.