A strange disease is linked to a mysterious hole that leads to an underground world: the Asylum. "Sleepers" come to this world to fight strange monsters and retrieve unknown resources. Now, a young man who dreams of being a hero has arrived at the Asylum.

As Shigure begins to settle into his new life as a Sleeper, he begins to wonder what he is good at and what he can accomplish at the Asylum.

Larry goes on a dangerous and illegal mission deep in the Asylum and forces Shigure to go with him.

Shigure delves into XO Leslie's past when a mysterious assailant suddenly ambushes him.

Now trapped in a time loop, Shigure struggles to unravel the mystery behind EL-Cee and Iceman's plans.

Shigure travels through time once more to save Vera and stop Iceman from destroying the world.