Asylum, a huge underground world, has been discovered in Antarctica. Shigure, a young man who volunteered as a Sleeper to investigate this hidden world, is assigned to a platoon led by Captain Vera. Shigue finds a group of musicians waiting for him, ready to join a risky and new mission.

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

Larry goes on a dangerous and illegal mission deep into the Asylum, and forces Shigure to come with him.

Shigure investigates the past of XO Leslie when a mysterious assailant suddenly ambushes him.

Shigure receives an order to kill Elsia, but gets distracted, neglecting his cooperation with Kobato during their mission. Leslie, who can't stand by just watching, tells him to strengthen his bond with Kobato for a month. Shigure learns more about Kobato's true situation

The day of the plot has arrived and the team heads into the Asylum; but when Hayden appears during the mission, things go very wrong.