The Summer Hikaru Died

It has been six months since Yoshiki Tsujinaka's best friend, Hikaru Indou, went missing in the mountains and returned a week later with no recollection of what had transpired. Certain that it is not the Hikaru he knows who came back, Yoshiki finally asks Hikaru about it. Suddenly, "Hikaru" reveals his true monstrous form and begs Yoshiki to keep it a secret, as he does not want to kill him.