sentences:  After Mirai had pulled the bus into Purgatory, Mirai forced everyone on the bus to kill each other until only one remained, with Sen as the only survivor (as she hid, with her mother being the final survivor who then killed herself so Sen could escape) which is why Anamnesis hated Rei, as she was the reason that she died in the bus crash.Still manipulating the girls to get more Idea, the demons give Mirai two prisons which are impossible to escape from and Mirai, hating the fact that Rei had made three new friends, traps Rei and Nanana in one, and Sen and Kokoro in the other, and then tells them to fight to the death and that only one of them could survive to fight Mirai.Still thinking that Kokoro killed her mother for no reason and "knew" about their relation, Sen murders Kokoro and escapes her prison, whilst Nanana eventually snaps after losing the last of her memories and Rei kills her in self defence, which allows her to leave her prison.