Summer Hikaru Died, Vol. 1 (light Novel)

Yoshiki and Hikaru were inseparable best friends in a quiet village. One summer, Hikaru died, but soon after, a being that looks exactly like Hikaru returns. Yoshiki knows this isn't his friend, but he can't bring himself to abandon the impostor. As strange incidents begin to occur in the village, Yoshiki must confront the unsettling truth about what happened to Hikaru and the entity that has taken his place.