|Romaji Title||Shōsha wa dare? (Nukiuchi tesuto)|
|English Title||Who's the Winner? (Suprise Test)|
|Airdate||Dec 17, 2014|
|Opening||Soushou Innocence by Maaya Uchida|
|Ending||The Last Party by 10th Year Class Black|
|Previous Episode||Episode 12|
Who's the Winner? (Suprise Test) (勝者はだれ？（抜き打ちテスト）; Shōsha wa dare? (Nukiuchi tesuto)) is the 13th episode of Akuma no Riddle which was unaired on TV thus only serves as an additional OVA episode which released together with the seventh Blu-ray/DVD volume on December 17th, 2014.
Nio Hashiri strands everyone in Myōjō Academy's 10th year's Black Class on a remote island and initiates a scramble game, in which all the other students must try to obtain a charm from Haru Ichinose using weapons found on the island without losing their own charms. As the game goes on, many students are eliminated and brought to the loser's area for a barbecue, resulting in a five-way struggle between Haru, Tokaku Azuma, and the remaining participants. In the end, Haru's charm goes flying and ends up in the hands of Mizorogi-sensei, who is declared the winner of the contest.