Yoshiki and Hikaru, boys who grew up together in a certain village.
But one day, Yoshiki becomes convinced that Hikaru has changed into something else.
A perfect "Hikaru" who looks exactly the same.
How could Yoshiki notice that he had changed?
What truth is he speaking? Furthermore, the townspeople are starting to notice the change and begin to take action.
The end of the book also includes a special short story that gives a glimpse into Hikaru's thoughts.