Itogami Island's tourist industry flourishes as the season of the annual Halloween Fest draws near. Kojou reunites with his childhood friend Tokoyogi Yuuma for the first time in four years, but Yukina and Asagi are not pleased to see the intimate friendship she shares with him. Meanwhile, when the Meyer Sisters suddenly appear at the Keystone Gate, the "witch of the void," Natsuki, finds herself in danger...

"Goodbye, Himeragi..." After hearing Kojou say this to her in a dream, Yukina begins to contemplate her future and the coming of the day when she may have to leave Kojou's side.