Asagi has been caught up in Kou's attack. Kojou and Yukina rush to save her, deciding to take her to Mimori's lab for treatment... but when they stop at Kojou's place on the way, another personality takes over Asagi's body.

Strange occurrences at sea result in Itogami Island becoming isolated. Nagisa continues to suffer effects from her previous exertions. A terrorist group known as Tartarus Lapse begins operations on the island.