Tozasareta nergal manga

Tozasareta Nergal summary:

Nergal has been accused and convincted of heinous crimes involving magic. As punishment, he was sealed and sent away to prison to await death for fourty days. The truth is though, he really is innocent! And, even though the guard Sunny befriended him...the boy's a total ditz! How will Nergal survive? At this rate, death may be more appealing than dealing with Sunny and the other prisoners and guards...