Strike the blood

Chaos erupts on Itogami Island as key personnel from the Gigafloat Management Corporation wind up assassinated, one after another. The culprit is the self-proclaimed Demon Sanctuary destruction group called Taartarus Lapse. Meanwhile, the soul of Avrora has been bleeding into Nagisa's consciousness, even as the mysterious girl "December" appears, who is the secret leader of Tartarus Lapse.