Hikaru ga Shinda Natsu

"So, Hikaru is no more... If that's true then..." Yoshiki and Hikaru are two boys who live in a certain village. They're the same age and have always been together growing up. But one day, Yoshiki noticed that "something else" has taken Hikaru's place. Even after learning of this, Yoshiki still wants them to be together. And so, his life with the "something" that looks like his friend begins. At the same time, strange incidents keep occurring in the village... (Source: Kadokawa, translated)