The Neuroi first appeared in 1939. Nobody knows where they originated from or what their ultimate goal is, but the truth remains that their attacks forced people out of their villages and cities. Humanity creates a new anti-Neuroi weapon known as the "Striker Unit" in order to take arms against them. This new technology increases and multiplies the ability of female magic-wielders by using the power of magic to battle enemies. To employ this gadget, young witches from all over the world have been brought together to form the 501st Joint Fighter Wing, also known as the "Strike Witches."