Tokyo, the year the world was supposed to end. Two people who had grown too numb to feel anything—not even grief at a friend's funeral—met a child named Mamiya. Before they understood what was happening, Mamiya had become part of their lives: a quiet presence, a source of warmth, an unexpected reason to get up in the morning. They did not realize until too late that the path Mamiya was leading them down had only one destination.