Nanbaka: The Numbers

From the introduction:

I can’t reveal its exact location, or its general location. That information is classified, at the highest level. Here’s what you’re cleared to know, somewhere out in the sea, on a remote island, is Nanba Prison. We utilize cutting-edge technology and elite guards from around the globe, to render this impregnable fortress the most secure in the world. If you thought about comparing the place to the one on Alcatraz, don’t, we’re better.