Oden Shinonome, who became a death row inmate due to a certain crime, is sentenced to "Excavation Sentence"—a stay of execution in exchange for mining "Bogosort," a precious yet dangerous ore. Together with her fellow death row inmate, Slumber, she is taken to the Gray Mall, a mysterious and massive ruin where Bogosort is found. In this demonic realm where outlaws and dangerous creatures gather, Oden-chan's life-or-death mineral-mining days begin! The curtain rises on a pop and thrilling prison comedy depicting the chaotic, topsy-turvy joys and sorrows of the prisoners!