We may be the only ones left in the world. In a world that was laid to a ruin with no one left, a young man, Ray, searches for people other than himself and Richie while she watches over him with worry. During this, a "secret" that had stayed hidden for 15 years is revealed by an invader from the skies. The young man, who is now alone, starts walking because of "a certain word." The curtain on a fantasy tale of people and machines in the near future rises here.

(Source: MANGA MILLION)

Note: Includes one extra chapter.