Air and sea transportation to Itogami Island have been cut off entirely. Meanwhile key personnel of the Gigafloat Management Corporation are being assassinated one after another. The mastermind behind this series of incidents is the selfproclaimed Demon Sanctuary Destruction group Tartarus Lapus. Nagisa is still suffering spiritual fatigue due to the awakening of the soul of Avrora. At this time she meets a strange girl who goes by the name December. Unbeknownst to Nagisa this girl is the leade