On the Path to Bravery in a Coward’s Paradise

This story follows Nanako Yomiuri, Ultimate Mystery Novelist, as she and 16 other people wake up to find themselves trapped in a strange place and at the mercy of a robotic monochrome… thing who informs them that the only way to escape is to kill one of their fellow classmates and get away with it.

How the hell did the SDRA2 cast find themselves in the Last Hope Sanctuary with only a few memories from their days attending Hope's Peak Academy?