On a late-night return home, Hikari Takadaki rides alone in a dimly lit, aging single-car train when the suspicious Jun Umadate boards as the only other passenger, stirring immediate unease. At the same time, Luna Amami steps off at her usual station only to be confronted by the menacing Kazuya Murakami. Taken to a hidden site, Luna soon finds Hikari already among the captors, her presence signaling the start of a shared ordeal.