Myojo Academy is a distinguished integrated campus equipped with a curriculum that ranges from elementary to college and strong connections to a large number of influential people. Despite its reputation, however, few in the public know about Myojo's Class Black, a secret, thirteen-student high school class that accepts enrollment at irregular intervals, formed for purposes aside from education. Namely, a game where twelve killers disguised as students compete to be the first to assassinate a target within the class.Tokaku Azuma, one of Academy 17's elite assassins, is chosen by her instructor, Kaiba, to participate in Class Black upon the request of Myojo Academy's Board Chairman. When she arrives, she meets the target, Haru Ichinose, who has the appearance and disposition of a regular high school girl, but it quickly becomes apparent that Haru is just as far from normal as anyone else in the class when Tokaku learns that she's lived her whole life as a target for assassination. In the process, Tokaku decides to go against the original plan and become Haru's sole protector against the remaining eleven killers of Class Black.Akuma no Riddle (meaning Devil's Riddle, but officially translated as Riddle Story of Devil) is a manga series written by Yun Koga and illustrated by Sunao Minakata. It received an animated adaptation produced by Diomedea on April 3, 2014 as part of the Spring 2014 Anime season.
Call Back: Episode 9 is this to episode 2. Just like before, it focuses on Isuke's assassination attempt and brings Tokaku's "curse" into focus. Even the short shot of Isuke's face in yellow light from episode 2 is brought back, except this time, it's on Tokaku. The relevant development here is that Tokaku gets over her curse. The episode is even called "What Dwells in Your Heart? (Make-up Exam)".
Chekhov's Classroom: In the class's first visit to the academy's botanical garden, Mizorogi teaches them about bullfinches after he hears one, mentioning that its chirp sounds like a whistle. Later, Tokaku hears the bullfinch through her phone while trying to talk to Haru who is being tortured by Takechi and figures out where she is.
The Clan: Haru's very existence is a problem to her very powerful extended family, explaining the assassins.
The Azuma family is a clan of assassins, to which Tokaku is the heiress.
Nio is revealed to be from a rival clan of the Azuma clan. They specialize in illusion and mind control to perform assassinations.
Cute and Psycho: Most everyone, but especially Takechi. Dear lord, Takechi.
Elaborate University High: Myojo Academy. While just how big it is remains a mystery (as some of the assassins wonder), it is a rich and powerful private school that provides all school levels, from elementary to university, and it has numerous connections to famous people and politicians.
Everybody Lives: In the anime, all of the characters survive, even the ones that apparently die onscreen from seemingly fatal stab wounds and poison.
Evolving Credits: The ending credits change for each episode, featuring an Image Song for the character prominent in the episode, and a matching animation sequence.
Exotic Eye Designs: The series has two normal eye designs: small pupils with fully-colored irises, and large pupils with only the lower half of the iris colored. Sometimes characters with the latter design temporarily gain the former when they get serious or surprised, but Shin'ya and, when she's in a killing mood, Takechi, gain a variation of the first kind that has two or three segmented rings around the pupil.
Expy: Between Takechi's long black hair, spider motif, Psycho Lesbian tendencies, and being both a rapist and serial killer, she's the spitting image of Hirasaka Hatsune.
Eye Catch: Featuring art of the same character featured in the ending, and some extra information about parts of the setting or other characters.
Foreshadowing: The manga and anime give out many hints with regards to later assassins, such as Nio always wearing full-body outfits, Suzu keeping her body fit and healthy, and Mahiru covering her face during the class' pre-school-play photo-taking.
I Want My Beloved to Be Happy: The length Hitsugi is willing to go in order to genuinely help Chitaru bring down Angel's Trumpet in the anime is considerable... considerable, because Hitsugi is Angel's Trumpet.
Idiosyncratic Episode Naming: Each episode's title is a riddle that Kaiba sends Tokaku within the episode, and is somehow vaguely related to the plot of the episode.
Marionette Motion: The robot/puppet replicas of the assassins at Hanabusa's tea party.
Masquerade: The Black Class is a rumor to most of the student body and a regular class to their teacher.
Mirror Match: The last episode presents two Tokaku's fighting each other. Interestingly, the real one is the one who's trying to kill Haru. The other one is Nio.
Mood Lighting: The fight between Tokaku and Takechi is shot with intense purple light. It diffuses as soon as Haru intervenes.
Something similar happens in the fight between Tokaku and Haruki. At first, the lighting is dark blue because the fight's in the dark, but when Tokaku gains the upper hand it suddenly turns bright red.
The Nose Knows: All assassins have a particular, unpleasant scent about them, according to Azuma. It's the fact that Haru smells different from them that first hints that she's the target.
Some if not all of the assassins have the same sense of smell that Azuma has, since Nio deduces that Azuma's not the target this way, and in the manga, Nio's scent makes Haruki more distrustful of her than others.
Overtook the Manga: The anime caught up with the manga around the middle of Haruki's chapter (or the middle of episode 5). Unlike other examples of this, though, the anime is based on the manga's original drafts, meaning it still follows the manga's plot despite the manga chapters not even being out yet. The manga, however, features bits of character interaction that the anime cut out (early examples being characters reacting to Takechi's bullying habits and Sumireko inviting Mahiru for tea and snacks).
Rack Focus: The anime uses this extensively, sometimes shifting the focus over three different objects in a row.
Resignations Not Accepted: Clover Home, Kouko's organization. This is the reason Kouko needed to use her wish to try to quit.
Riddle Me This: Kaiba regularly sends Tokaku riddles through her phone. He seems to use them to gather some kind of information about Tokaku's development, and claims that Tokaku might be punished if she doesn't answer them.
Suzu also has this as a part of her aforementioned plan.
Ring Ring Crunch: A variant in episode 3. When Takechi is woken up by an alarm clock, she brings her fist up to silence it... only to thoroughly crush Shiena's glasses instead.
Romantic Two-Girl Friendship: The relationship between Hitsugi and Chitaru. Episode 6, and their character song during the ending, calls into question if it really was this, or if they felt full on lesbian love.
Tokaku and Haru could count as well.
Rule of Seven: Tokaku's first password attempt to diffuse the bomb strapped on Haru is 7777 and the other two have 7 on them; all of these happen in Episode 7. To make things interesting, said episode stars the Student No. 7 Suzu, whose birthday is 7/14, and is 7th expelled.
Running Sequence: The fourth ending mainly features the focus character walking briskly to the beat of the song.
Sadistic Choice: "One in the water, in exchange for something valuable." Turns out that it's a keycard for the cage Tokaku gets locked in, containing the last clue. Using the card destroys the clue. So now Tokaku has to choose between saving herself, or saving Haru, and vice versa for Haru.
School Play: For Myojo's Anniversary Festival, Class Black puts on Romeo and Juliet, with Chitaru as Romeo, Hitsugi as Juliet, and Shiena directing. The anime version has a twist in that the characters playing Romeo and Juliet actually die for real in front of the audience, while masking it as part of the act.
The Seven Mysteries: Myojo Academy has seven wonders, but only three of them are mentioned, and only one of those three are investigated.
Shout-Out: Episode 7, where Shuutou sets up a Riddle Me This situation, has a couple of shout outs to Batman: The first combination Tokaku tries is 7777 (in Japanese, nana nana nana nana), and one of the cards used for the clue is a Joker.
Sinister Surveillance: The entire academy is being watched by a mysterious woman (and sometimes Nio, through a tablet-like device) through several hidden cameras.
Slipping a Mickey: Isuke serves drugged tea to Haru. It doesn't work thanks to all the surgeries Haru has been through.
Smashing Watermelons: Nio suggests doing this in episode 7, and Sumireko asks if they can use whatever weapons they want (being assassins), bringing out a sub-machine gun. Tokaku ends up slicing open the watermelon to find the first card they need for Suzu's game.
Stealth Pun: The term "black" here has multiple meanings in Japanese and regular slang, ranging from "elite" (see "black belt") to "illegal activity" (see "black company").
Twenty Minutes In The Future: The anime/manga is likely to be several years into the future. Myojo Academy has advanced technology such as touchscreen bulletin boards and tablets that can be linked to surveillance cameras. The fact that Haru's year of birth is labeled as 20XX could support this trope.
Unexplained Recovery: Three characters; Hitsugi, Haru, and Nio, are "fatally" stabbed, but fully recover with no signs of lasting damage. Aside from that, Chitaru seems to be fine sometime after drinking a whole vial of poison, and Sumireko somehow managed to fully recover after falling over 90 floors down a building. Out of all of them, only Haru's case provides any semblance of explanation: titanium in her ribs.
Wham Episode: Episode 6. It breaks the assassin-of-the-day pattern of the previous episodes by eliminating three assassins at once and (seemingly) presents the first instance of Character Death in the series, killing off the two assassins that were put in focus while making parallels with Romeo and Juliet to emphasize the circumstances. By the end of it all, even Tokaku and Haru were shaken. The final episode reveals that both of them survived, but it's still one of the most shocking moments in the series.