Ever since the fungus hit, Kouji and Kouichi have been living in what little remains of Tokyo. They end up meeting a mysterious boy named Tomoki who needs to leave the city. Will they leave the safe zone to explore their once homes and find out where exactly their parents and friends are?

When Kouichi is found unconscious, drugged and naked outside, the young male's life begins to take a startling turn for the worst as he begins to see his attacker harming people he meets randomly. However, when they actually are attacked, it's usually the next day. Will he be able to use his new powers to stop his attacker and save anyone from what happened to him?

Duskmon has always followed Kouichi, keeping in the shadows as he grew up. What happens when Duskmon suddenly reveals himself inside Kouichi's bedroom at the age of 17? And, why is he talking about a promise?