A new fighter squadron is established as humanity's conflict with the Neuroi—a mystery, hostile extraterrestrial species with weapons of incredible power—continues across Europe and Africa. The 502nd Joint Fighter Wing, popularly known as the Brave Witches, operates on the eastern front, combing Orussia's ice expanse for extraterrestrial invaders. However, on her route to the squadron's headquarters, one of the Brave Witches receives terrible injuries, making her unable to engage in any missions. As a result, Hikari Karibuchi, her sister, volunteers to take her place. Despite the fact that she lacks any particular talents or strong magical capabilities, she is eager to live up to her new companions' expectations and show herself worthy of the title of Witch.