Haibane's lives are eventually drawn toward their , or in the English-language versions, "Day of Flight." This day approaches when the Haibane in question has overcome certain internal trials and is ready to move on. Their halo begins to flicker and dim. Finally they depart, alone and unannounced, for an ancient ruin in the Western Woods, where they pass over the city walls in a beam of light. Their halo is left behind on the ground and no longer glows. The other characters experience this much as they would an ordinary death—no one knows when it will happen, or what lies beyond the wall, and those left behind feel the loss of separation. Nevertheless, Leaving the Nest has a positive connotation, and most of the Haibane believe that life beyond the walls is somehow higher or better than life in Glie, and that friends can reunite there. It's later revealed that this passage is not certain and has a deadline; the flickering of the halo serves as warning that the moment of truth approaches. If a Haibane fails to overcome their trials by then, they "fall" instead. The Haibane loses their wings and halo and is forced to grow old and die in isolation.