Nagisa has collapsed! Kojou rushes to the hospital, but suddenly a mysterious girl appears, and she looks just like Avrora, the former Fourth Primogenitor. She backs Kojou into a corner--but is she the real Avrora?
Through this encounter, Kojou regains his lost memories, what will he remember?
Finally, Kojou's past and the secrets of the Fourth Primogenitor are revealed!