Kinda feel like she might turn out to not disappear by virtue of turning out to be Shimizu's reanimated corpse or something. 'Cuz presumably the people Naito killed are going to stay dead, right? So why can't someone he brought back to life stay alive? And I think that it would be kind of fitting if he was sort of successful in that regard, of bringing her back, just as the person he knew, but rather the one Tasuku (his foil) knew.