The Decagon House Murders

Written by Yukito Ayatsuji

Mystery

A few weeks ago I was reclining on a couch playing a murder mystery game with my friends. The game takes place on a tropical island where a class of high school students need to solve a string of murders amongst themselves in a series of mysteries. One of these murders features a puzzle about a secret room called the Octagon where the presumed murder weapon was acquired. The puzzle had a deceptively easy request to make of us; spot the Octagon in the picture, nothing more to demand, a ten second task surely. After all, we had three other buildings in this murder mystery; a square building, a cylinder building, and a hexagon building. Why would it be difficult to find the Octagon?

Well, first take a look at the picture provided to us, dear reader, and see if you can point out where the Octagon is.  

The perceptive among you note that there in fact is no Octagon in this photo.

There is in fact no discernable octopus-centered shape at all in this photo. The next moments were definitive pandemonium. My friends and I languished in this 8-sided Sisyphean purgatory for entire minutes, screeching at absent gods for the true answer as to where our muse lied - that desirable Octagon and the end of this shape-shuffling spectre.

Eventually we did figure out what the Octagon was.

But the burned memory remained, fried onto my frizzled synapses whenever I closed my eyes.

It was a few weeks later when I thought of the Octagon again while browsing online.

A social media post showed a book called the Decagon House Murders and on that post was a ten-sided drawing of a map. Two sides off from eight. A map of a shape with ten rooms. Two rooms off from eight. A map in the shape of a decagon. Two sides off from an octagon.

A twinge of irritation in my heart, I swore then that I would not be bested by basic geometry again.

This was my opportunity, my journey, to best what I barely could before; to one-up a decagon, along with the dastardly octagon.

I looked online and I found the excerpt of the book; 

a group of university students

stuck on an island

trying to solve a spree of murders

Coincidence? No, this could not be. Two pieces of murder mystery media perfectly aligned to match; students, stuck on island, spree of murders, one larger mystery, one geometric shape.

I would not falter; this time, I would not be denied!

I ran to my local library, breezed through the book, questioned what allegories and symbolism laid inside, finished it, realized the blatant gap of symbolism which I originally expected, and thus the rest of the review was born.

What Is The Decagon House Murders?

The Decagon House Murders is a murder mystery where a group of university students who are part of the university's mystery book club take a trip to a remote island off the coast of Japan. For some context the island was previously owned by a famous architect named Nakamura Seiji, who lived on the island with his wife, a pair of married servants, and a gardener. Six months ago he was found burned alive, his wife and servants dead, and the gardener missing and presumably at large. About one year ago, Seiji's daughter Nakamura Chiori died while attending the university's mystery book club party due to a misfortunate mix of alcohol and a chronic heart condition.

The book is divided between two points of view. One is the group of university students on the island who are staying at the only building still intact after Seiji's death, a decagonal house aptly named the Decagon House.

The other point of view is from an ex-member of the book club named Kawaminami residing in Japan who has received a threatening letter from the dead Nakamura Seiji accusing him and all the other mystery club members of murdering Nakamura Chiori. He decides to investigate and spends his time in Japan trying to figure out who sent the letters.

The book goes through a step-by-step, day-by-day narrative where we jump between Kawaminami and the rest of the cast as the murders slowly progress one-by-one. 

The book has a manga adaptation, however I will not be covering it as I have only read the written novel, and the only significant change to the plot is how Chiori died. 

Who Is The Author?

 The author is part of the new traditionalist writing movement in Japan, and particularly is fond of closed circle murder mysteries and the classic whodunnits, with limited suspects, a set of motives, isolated locale, and a prevalent murder placed at the very beginning. What this means is that the murder mystery suspects are all people you meet in the story upfront; no one hiding in the background. It also means the motives are usually clear-cut and personal for the murderer.

I will be honest; I like this style of mystery. The appeal is clear. I also like mysteries where it is more "slow-burn", with the characters being built up over long periods of time with the occasional murder.

He is one of the founders of the Honkaku Mystery Writer's Club of Japan, and has actually written the Decagon House Murders as part of a "series" of mysteries where murders occur in a locked house. He has also written a popular murder mystery manga called Another, a fact that I was initially oblivious to and surprised by.

What Is The Symbolism (And Lack of It) + Some Extra Details

Before going into the themes, please note these discussions and analysis's are centered on the English translation of the book. Translation is not a 1:1 interpretation and my analysis of the themes comes from my own interpretation of the translated sentences, some of which were more ambiguous than others in their phrasing. The following themes discussed all weirdly tie together while remaining separate:

It's Not Actually In Order

Author's Partial Self-Insert and Inspiration

Social Commentary

The Lack of Social Commentary

Foreshadowing That Is Also A Spoiler

At the beginning of the book we start with our point of view coming from the murderer, who says that they will kill every last one of the victims in order, one by one. This does not mean that the murderer is planning on killing certain people in a certain order, it means they will kill their victims one at a time. In order does not mean that the killer has a planned method of who will die first, second, third, etc... I did not realize this until halfway through the book. My friend didn't have this problem, so maybe this was just a me issue. Regardless I'm putting it here just in case.

Moving on, one of the characters in this book is named Ellery, and while I do not know for sure, my friend and I have the sneaking suspicion that he partially acts as a self-insert character for the author. Ellery acts as the detective of the novel and the other characters regard him as snobbish in tastes of mystery literature, criticize him for holding a cold and callous stance towards the death around him, and is frequently subject to the butt of scrutiny regarding him being a potential murder suspect. He embodies the archetype of the incompetent detective and is seen as callous by the rest of the cast.

So why do I think he is partially a self-insert character? Well in spite of the negative light the character is written in, Ellery is particularly fond of locked room mysteries, especially those with a clear culprit, suspects, and locale. Essentially, whodunnits and closed circle murders, same as the author. Ellery also gives a critique to most modern mysteries (or at least modern in the 1980's), complaining that modern forensics make it nigh impossible to set a murder mystery in the modern day without some external isolating incident (rain, a storm, disabled communication, or being isolated on an island). This likely aligns with the authors preference for closed circle whodunnit mysteries, which while not relevant to the other themes I will be discussing is still a fun detail I noticed.

Another part of the story is that it heavily references Agatha Christie's "And Then There Were None", where a group of people are all accused of committing a past murder and are killed off one by one. This reflects the book, from the accusation of the group committing murder, to them then being killed off one by one. The ending of the referenced book is spoiled, although the identity of the culprit isn't revealed, but just in case you don't want to know maybe read "And Then There Were None" first. 

Now as I said before, Ellery also complains about a few things that the characters chastise him on. One of these things is that mysteries in the modern day focus too much on prevalent social issues; abusive relationships, politics, inequalities, power dynamics, workplace abuse, Ellery believes all of these shift the story away from the traditional culprit-with-a-motive style of writing. Hearing this, of course, you may remember that Ellery is seen as "stuck-up" by the other members of the cast and because of this you may mistakenly think, like my friend and I, that Ellery's diatribe is the authors way of foreshadowing the opposite - foreshadowing the mystery WILL revolve around a prevalent social issue, one which frequently reappears throughout the book.

While reading I kept this comment from Ellery in mind, believing it to be a subtle hint towards the motive and killings, and as such looked for subtext in the book while I was reading.

Spoilers for significant chunks of the book by the way!

In the novel, I originally thought misogyny was a key theme. Some examples include:

1. The murderer intending to kill the women of the group first. While one of these murders makes sense as the "murdered-to-be-in-question" would best understand the killer's motivation and likely be able to identify who the killer is the moment the murders begin, there isn't really a reasoning as to why the other woman was intended to be murdered immediately after; considering the killer plans on poisoning almost everyone in the group, and there is another male character who can easily identify poisons and how someone died, why not target him? This point honestly doesn't hold as much ground as I am making it out to be, as the remainder of the order of the murders committed are done solely through chance-based time-bombs, but it's still something I thought about when trying to identify social issues in the book.

2. A decent chunk of the characters in the group are casually misogynistic. The women are the ones who are serving food and coffee to everyone throughout the entire novel, even after the murders start. One character in particular is guilty of this (Carr), but he's written to be intentionally an intrinsically unlikable and intolerable character who we as an audience, and the characters in the story, dislike.

3. The backstory of Seiji, the previous owner of the island, originally decided to live on the island because he was afraid his wife was cheating on him with his brother. Shepherding your wife away to a geographically isolated island because you are worried she might cheat on you is, as you may imagine, not vindicative of a healthy relationship. Also, when Seiji's daughter dies, he sexually assaults and murders his wife. 

4. Chiori's death is originally caused by her being pressured by her friends into excessively drinking at a party. The murderer claims that Chiori would not have ever agreed to drink, and was likely pushed to do so by everyone else. 

5. The motive behind these killings in the first place is because the killer states that they and Chiori were secretly in love. Except it wasn't publicly known. And I doubt Chiori even returned the killer's feelings because the murderer states that (and I am paraphrasing here) "they chose to have a love without words, staring from afar, to avoid any embarrassment that may come about if their love became public". The killer tries to justify that they were in love because they had "a couples ring", which was a ring that had both of their initials carved onto it. Here's the thing though - remember that one woman who died first in the murder spree? The one who had to die because she would have immediately know the motive of the killing? She is the one who is given Chiori's couple ring after Chiori's death. She was also indicated to be the closest to Chiori as she is the only one at the island specifically to grieve her death, is one of the few in the group who knew her relation to Seiji and her family, and is the only one in the group who actually was invited by Chiori to the island previously. So, I don't exactly trust the killer's reasoning of "we were in love we just couldn't publicly show it or talk about it."

Spoilers -------- OVER!

With all of this in mind, I read a decent chunk of the book expecting to uncover a resolution that commented on the effects of misogyny in the modern day (or 1989, if you count when the book was written) given the information provided of Seiji's wife, Chiori, and the attitude of some of the club's members (primarily Carr). However, you may be surprised to learn that there is no moral regarding social issues in the story. Ellery's complaint, the points I listed above, all of them come from simple one-to-two sentences used to set up future motives and preface the background of the island for the story. Ellery's complaint was not intended to be interpreted as either a red herring as to how the book would conclude, or as a hint that the book will be covering social issues. It is simply a case where my friend and I read the line, overanalyzed it, and proceeded to read several lines of the book way more in-depth than the author probably intended.

This whole section wasn't really anything more than a ramble about how I failed in a way most mystery books fail; ignoring Occam's Razor. In this circumstance, the meaning behind the book, did not exist; it's existence was solely in my mind due to my overinterpretation of the novel's elements. 

I still thought that I should write it down here however because if my friend and I misinterpreted Ellery's line as foreshadowing then it's likely someone else will too, and end up very confused two-thirds of the way through the novel trying to dissect the murder motive.

The final piece that I would like to discuss regarding the book is also a piece of foreshadowing, and this time it is probably intentional.

Spoilers, again. Big ones; literally spoils who the murderer is so... 

While my friend was reading, they figured out the murder early on.

By this I mean, I realized who the murderer was, and then had two back-up suspects I could pivot to if they ended up dying.

My friend immediately figured out the killer, and the twist of their murders.

The murderer -

BIG SPOILERS AHEAD IM SERIOUS DO NOT KEEP READING IF YOU DON'T WANT TO KNOW

okay still reading on ahead? good.

- has an alter ego on the mainland. Everyone in the mystery club uses fake pen names when meeting because they like to be dramatic, a sentiment I kind of understand. In the prologue, the murderer monologues about God, and fate, and justice, and so on. However as part of their alibi the murderer claims that they are painting a picture of Buddha, an activity mentioned and brought up several times through out the book. This foreshadows the identity of the murderer. Furthermore, the murderer requests divine punishment if their actions are wrong, an idea emphasized by them: a, throwing a bottle with their murder plan on it into the sea, b., the lead detective on the mainland being a priest, and c., at the end of the novel both the priest and the bottle end up in play. 

This is just a part of foreshadowing that I personally didn't notice that DID hint at the identity of the murderer.

The final thing I want to mention is the manga adaptation of the book. I have not read it, or know anything about it, except for a change in Chiori's death. In the manga, Chiori died after the mystery club boat capsized, and someone took her life jacket to save another drowning member. This was allegedly (according to TV Tropes) done to make the rest of the members of the club more culpable in Chiori's death. I disagree with this change as I feel the original cause of death was messy, blurred, and ambiguous in culpability, making all of the club members much more culpable even as bystanders (and the murderer having a clearer justification against the entire group rather than a single member). 

Overall, read this book. It's considered a classic for a reason and while I thought some plot points of the murderer's plan were unnecessary (and trust me, I can rant for a long time about what I liked and didn't like about a murder mystery, how the murderer could've done the crime better, and speculate who will live and die), it was a simple, enjoyable experience.