A signal from a data recorder that an investigative unit left behind in an area that was engulfed by the Lightless Realm ten years ago had been received. It was that of the unit that Aoshi had once piloted. Harboring complicated emotions, Akashi heads to recover the recorder together with Heito. As soon as they enter the Lightless Realm, the two lose sight of each other. Immersed in abnormal levels of tension, Akashi and Heito eventually come to cross paths with their pasts.
