Growing up without a father, Seijuro, enters a forbidden tomb with his younger brother, Ren, hoping to find valuables to support their struggling family.
Instead, Seijuro unknowingly breaks open an ancient seal, releasing powerful entities, the Nyxion, formed from being corrupted by dark matter or Tenebris.
The consequences are immediate and devastating: Ren is taken and transformed, leaving Seijuro powerless to save him.
Seijuro is captured by the Fear Foundation, an organization of mages who protect humanity from supernatural entities known as fears, manifestations born from extreme trauma.
Rather than killing Ren outright, the Foundation condenses his soul into a weapon, preventing him from remaining as a mindless monster. Though Ren still exists, his body is gone, binding him permanently to Seijuro’s guilt.
Judged responsible for unleashing a greater threat, Seijuro is given a choice: submit to the Fear Foundation’s brutal training or be executed. Clinging to the hope that he can one day restore his brother, Seijuro accepts.
As he begins his training under the Captains, he learns that not all of them share the same ideals, some believe humanity itself must be erased to prevent fears from ever forming.
With a world full of different ideologies, only time will tell which path Seijuro will take.