光が死んだ夏 [Hikaru ga Shinda Natsu] Series by Mokumokuren

It has Hikaru’s face. It has Hikaru’s voice. It even has Hikaru’s memories. But whatever came down from the mountains six months ago isn’t Yoshiki’s best friend. Whatever it is, it’s dangerous. Carrying on at school and hanging out as if nothing has changed―as if Hikaru isn’t gone―would be crazy. .. but when it looks so very like Hikaru. .. and acts so very like Hikaru. ..

When Yoshiki struggles to accept the new Hikaru, he’s given a glimpse of what’s lurking inside his best friend. But will that be the final straw that drives Yoshiki away for good?

A strange man arrives to investigate the strange occurrences that seem to be happening more and more frequently around the village. Everything seems to be linked to the mountain where Hikaru died and “Hikaru” came from. ..

Two boys grew up together in a certain village—Yoshiki and Hikaru. One day, Yoshiki became sure that Hikaru was no longer himself. He resolved to accept the new “Hikaru,” whatever happened to his friend. But now he’s decided to research the history of “Nounuki-sama” and Kubitachi to understand what this creature truly is. The situation evolves unpredictably, outside the boys’ control. Who will make the next move, and what will they find?

Yoshiki has resolved to walk alongside the “something” that replaced his friend, Hikaru. But changes begin to appear, not just in the village, but also in the impostor himself! As they sense their current lives moments from crumbling down, the boys continue their investigation into “Hikaru’s” identity. The history of Kubitachi, the truth of “Nounuki-sama,” and the “Indous’ sin”. .. what will the answers to these mysteries mean for “Hikaru” and Yoshiki? !