The High King Dragon Z-ARC brought about the end of the world. Reo speaks about the day the world was split into four. Once, a girl named Rei stood against Z-ARC in Reo's place and he says that her feelings are in Reira, but Reiji recognizes it as a scheme his mother, Himika, told him about. When he sees the overwhelming rage Reiji feels over the tragedy, Reo asks for Reiji's help with Revival Zero...
It simply isn't possible.