A squad of prisoners and their guards are sent to investigate a mysterious island. They get stranded there and must rely on each other to survive the island's mysterious and monstrous residents.

In the Edo period of Japan, a select group of convicts awaiting execution are offered the chance to be pardoned and freed the Shogunate of Japan if they go to investigate an island recently discovered southwest of the Ryukyu Kingdom. the convicts are accompanied by elite guards to ensure they won't escape. Once they reach there, they find themselves overwhelmed by the island's residents, a host of monsters and their creators, a group of immortal beings. Now the convicts and guards must work together to stop the immortals and escape the island.