Magic Prison (魔監獄, Ma kangoku) is the 7th episode of Muhyo & Roji's Bureau of Supernatural Investigation anime series.
Bico, a magical tools master who attended the Magic Law School with Muhyo, suddenly appears at the Bureau one day. Bico asks Muhyo to come to Magic Prison No. 18, a prison where very powerful spirits are sealed. A talisman that had been used to seal the bottom level, where the most dangerous spirits are kept, has been ripped off its door... and Bico feels responsible as the one who had made the talisman. Muhyo agrees on the condition that Bico will owe him one later, and they set off for the island that houses the magic prison.