Oni are a great calamity to the human race. Oni are a natural disaster. Oni were once human, the shadows of their former selves. Since ancient times, there have existed people with the latent ability to exorcise and seal oni. People call them the exorcist shrine maidens... Recently, the beasts have been cropping up with unusual frequency... And so, the Oni Killer Maiden Squad has been searching for those with the power to destroy them. Mikoto, Honoka, Kikyou, and Yae will exterminate the monsters without exception. But when an ancient threat appears, the Impregnating Oni, can the girls stop them? ...Or will they regain their power?