Unaired episode 13 of Akuma no Riddle released with the seventh Blu-ray/DVD volume. The special will be previewed at a screening in Tokyo City on November 22, 2014. The BD/DVD will be released on December 17, 2014.
9Anime is the best site to watch Akuma no Riddle: Shousha wa Dare? Nukiuchi Test
SUB online, or you can even watch Akuma no Riddle: Shousha wa Dare? Nukiuchi Test
DUB in HD quality. You can also find Diomedea
anime on 9Anime website.