History Literature / TheDecagonHouseMurders

See ''{{Literature/Another}}'', written by the same author.

The debut [[MysteryFiction mystery novel]] of Creator/YukitoAyatsuji, published in 1987 and riddled with references to Creator/AgathaChristie's ''Literature/AndThenThereWereNone''. It has a manga adaptation.

* HollywoodHomely: In both the novel and manga, Orczy has very low self-esteem related to her appearance, especially in comparison to the traditionally beautiful Agatha. In the manga at least, she is in fact very cute, and the male members of the mystery club express interest in her; she just dresses unflatteringly.

* TheBadGuyWins: [[spoiler:Van, or Morisu, successfully kills the six club members that he blames for Chiori Nakamura's death and frames Ellery as the culprit. However, while he has fooled the police, Kiyoshi Shimura might be onto him, and the book ends with Morisu asking a boy to give his written confession over to Shimura, so he may ultimately not get away with his crimes.]]

* TenLittleMurderVictims: Seven members of a university mystery literature club visit an island where a gruesome massacre took place sometime before and start being killed off themselves. Two of the club's other members, not aware of the danger their friends are in, investigate the prior murder on the mainland. It turns out that one of the club members is moving back and forth between the island and the mainland to give himself an alibi, and has let everyone else think only six people went to the island.
* TomatoSurprise: "Van" ( who takes part in the TenLittleMurderVictims event on the island) and Kyoichi Morisu (the [[PhoneInDetective Armchair Detective]] who helps out the narrator on the mainland) are the same person. All of the people on the island and the narrator of the mainland section know this, but nobody realizes it's relevant to the case because Morisu lied and told everyone except the island goers that he wasn't going to the island in order to give himself an [[TheAlibi alibi]].

* AdaptationalIntelligence: [spoiler: Junya [[InSeriesNickname "Ellery"]] Matsuura]] is a textbook DecoyProtagonist who, despite spending the whole story trying to solve the case, draws completely the wrong conclusion and [[spoiler: is [[InTheBack backstabbed]] by the culprit immediately after blithely inviting them to go hunt for a non-existent true culprit together]]. In the book's official manga adaptation, however, [[spoiler: Ellery]] successfuly identifies the true culprit, using [[PercussivePickpocket Percussive Pickpocketing]] to take away their knife and delivering a lengthy [[TheSummation summation]] explaining how they knew that they were the true culprit and the false conclusion their novel counterpart drew was wrong. The only thing stopping them from ending the story ahead of schedule is [[spoiler: the culprit [[TamperingWithFoodAndDrink drugging their coffee]] ahead of time]].

See ''{{Literature/Another}}'' for another novel by the same author.

The debut MysteryNovel of Creator/YukitoAyatsuji, published in 1987 and riddled with references to Creator/AgathaChristie's ''Literature/AndThenThereWereNone''. It has a manga adaptation.

* HardToAdaptWork: In UsefulNotes/{{Japan}}, the novel is synonymous with this trope for spoiler-y reasons. The culprit is someone who was seen on both the mainland and [[TenLittleMurderVictims the island]], and the fact that these two characters are [[TwoAliasesOneCharacter the same person]] is meant to be a shock to the reader, but isn't to any of the characters. Naturally, letting the audience actually see the killer's face or hear a voice at any point would immediately give it away. The book went unadapted for 32 years before a manga adaptation was published [[spoiler: where the culprit's resemblance [[OnlySixFaces would stand out far less.]]

* TomatoSurprise: "Van" ( who takes part in the TenLittleMurderVictims event on the island) and Kyoichi Morisu (the [[PhoneInDetective Armchair Detective]] who helps out the narrator on the mainland) are the same person. All of the people on the island and the narrator of the mainland section know this, but nobody realizes it's relevant to the case because Morisu lied and told everyone except the island goers that he wasn't going to the island in order to give himself an [[TheAlibi alibi]].]]

* HardToAdaptWork: In UsefulNotes/{{Japan}}, the novel is synonymous with this trope for spoiler-y reasons. The culprit is someone who was seen on both the mainland and [[TenLittleMurderVictims the island]], and the fact that these two characters are [[TwoAliasesOneCharacter the same person]] is meant to be a shock to the reader, but isn't to any of the characters. Naturally, letting the audience actually see the killer's face or hear a voice at any point would immediately give it away.]] The book went unadapted for 32 years before a manga adaptation was published [[spoiler: where the culprit's resemblance [[OnlySixFaces would stand out far less.]]