When humanity is pushed to the edge of despair by an alien menace known as the Pillars, a self-proclaimed deity named Odin appears and grants the people the power of "Valkyries"—warrior maidens who pilot vintage aircraft called Hero Wings. Claudia "Schwertleite" Bruford is the ace of the European Valkyrie Wing. After Japan's S-class Valkyrie dies in combat, Claudia is transferred to Japan as her replacement. However, carrying a dark history of being the sole survivor in every mission—which earned her the nickname "Grim Reaper"—she suspects she already knows why she was selected. Bracing herself to be ostracized once more, she arrives at the Tateyama Valkyrie Wing. Little does she realize that her new comrades are a group of eccentrics who have absolutely no intention of accepting her ominous nickname!