"Hikaru's" unexpectedly violent encounter with the mysterious hamster-toting Tanaka only worsens his already weakened condition. Without knowing Tanaka's intentions, the boys must act quickly to uncover the mountain's secrets. Investigating the Indou family's "sin" will be difficult now that Hikaru's dad has passed, but they may be able to get some answers out of his closest friend-if Yoshiki's father is willing to talk...

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?!