Welcome to Nanba, the world's largest and most impenetrable prison. Locked away in Cell Block 13 are four inmates - pill-popping Nico, burly food-loving Rock, gambling charmer Uno and Jyugo, who was born at Nanba and has made more escapes than any other prisoner there - who provide more than enough trouble for the tough Officer Hajime. Follow them and their numerous adventures within the walls of Nanba.