Reality was never what it seemed.
When a student mysteriously disappears without a trace, three friends begin searching for answers inside their school late at night. What starts as a desperate investigation soon turns into a terrifying discovery — hidden portals, strange energy spreading through the walls, and creatures that should not exist.
Behind the surface of their world lies Ura Sekai — a hidden realm connected to fear, darkness, and unimaginable power.
As the boundary between worlds begins to break, the boys are pulled into a deadly conflict far beyond human understanding. Guided by a mysterious monk who knows the truth behind the hidden world, they must uncover ancient secrets before the gate fully opens.