Yoshiki and Hikaru, boys who grew up together in a certain village.

One day, Yoshiki becomes convinced that Hikaru has changed into something else.
A perfect "Hikaru" who looks exactly the same.
However, feeling that there is an inner side that is clearly different from that of a "human", Yoshiki approaches "Hikaru" and spends his days as usual.
As the distance between them narrows by expressing understanding, an incident occurs that makes them realize the unbridgeable difference in values ​​between them and those who are not "humans".
The book also includes a special short story that gives a glimpse into the daily life of the class.