On August 31, three years ago, a huge mothership of the "Invaders" suddenly descended on Tokyo, and the earth seemed to be about to usher in the end of the world. As time passed, despair gradually integrated into daily life, and the huge mothership still hovered in the sky today. At this moment before the end of the world, the youth of two high school girls, Koyamamonde and Nakagawa Houlan, was just about to begin.