The world has suddenly been twisted into a dark night. People have been wiped from existence entirely and the only man left on Earth, Leon Hikara, is left to pick up the scraps that have been left by humanity. As amnesia had struck him due to an accident, he has to not only find ways to leave a final mark on Earth, but also to find himself and his past. With a constant battle with depression and self doubt, Leon does his best to deal with the loss of humanity and make new experiences.