Hotarubi no Tomoru Koro ni

Hotarubi no Tomoru Koro ni (蛍火の灯る頃に) is an horror manga series written by Ryukishi07 and illustrated by Nokute Koike. The story follows the Tadamura family as the family meets in the remote village of Hirasaka. The story is preceded by a short prologue entitled The First and the Last Gift.

Plot
It's July 2016, and the Tadamura family gathers in the Hirasaka village for the funeral of the grandmother and head of the family: the young man Yukito, his step-sister Yue, his father Masashi, his uncles Nobuteru and Tsunemasa, and his cousins Terumi and Teruya, all come to pay their last respects.

But on that evening, Yue witnesses an incomprehensible scene: the grandmother's dead body starts to move and disappears into the night! The morning after, the family wakes up in a strange world, seemingly cut off from reality, where two suns shine...

Chapters

 * 00. The First and The Last Gift
 * 01. Coming Back Home
 * 02. Fog
 * 03. Assault
 * 04. Curtain Rising
 * 05. Chapter 5
 * 06. Hell
 * 07. Fissure
 * 08. Apparition
 * 09. Reunion
 * 10. Discovery
 * 11. Journal
 * 12. Transformation
 * 13. Chapter 13
 * 14. Night Feast
 * 15. Refuge
 * 16. Yohei
 * 17. Chapter 17
 * 18. Fireflies
 * 19. Ascent
 * 20. Escape
 * 21. Future

Volumes

 * 01. Hotarubi no Tomoru Koro ni: Volume 1
 * 02. Hotarubi no Tomoru Koro ni: Volume 2
 * 03. Hotarubi no Tomoru Koro ni: Volume 3
 * 04. Hotarubi no Tomoru Koro ni: Volume 4