Another Rebuild post, which serves as an introduction post to some of the longer series I discuss here. Links to all related reviews, short introduction, discussion on general series tropes, it's all here. This time, one of the more famous series of contemporary Japanese orthodox detective fiction.
Yakata series (Author: Ayatsuji Yukito)
Jukkakukan no Satsujin (The Decagon House Murders) 
Suishakan no Satsujin (The Water Mill House Murders) 
Meirokan no Satsujin (The Labyrinth House Murders) 
Ningyoukan no Satsujin (The Puppet House Murders) 
Tokeikan no Satsjin (The Clock House Murders) 
Kuronekokan no Satsujin (The Black Cat House Murders) 
Ankokukan no Satsujin (The Darkness House Murders) 
Bikkurikan no Satsujin (The Surprise House Murders) 
Kimenkan no Satsujin (The Strange Masks House Murders) 
Kirigoetei Satsujin Jiken (The Kirigoe Mansion Murder Case) 
Ayatsuji Yukito Satsujin Jiken (The Ayatsuji Yukito Murder Case) 
Spread all across Japan are the mansions built by genius architect Nakamura Seiji. While all of his creations have different themes, these houses all have two characteristics. One is that Nakamura Seiji loved building gimmicks in his mansions: each of them are full of secret passages, hidden rooms and other surprises. The second characteristic is that his creations somehow always seem to attract death. Violent death. Nakamura Seiji died in 1985 on his own private island Tsunojima, but his legacy would remain lethal: after getting involved with the events in The Decagon House Murders, where a group of students was murdered on the island in a And Then There Were None style, Shimada Kiyoshi tries to learn more about the haunted houses and travels around Japan to see what more evil Nakamura Seiji's creations have led to.
I'll first note that The Decagon House Murders, the first book in the series, is a very important book in the history of Japanese detective fiction, being the first in the so-called New Orthodox movement, which meant a re-, and deconstruction of the classic puzzle plots of lore in the modern age. As this post is meant to be a general introduction to the series, I refer to the review for more details on the meaning of The Decagon House Murders within Japanese detective fiction history. In terms of series continuity however, it might be interesting to note that The Decagon House Murders wasn't planned as a series: Shimada Kiyoshi in particular wasn't created as a series detective and this entry in the series might feel a bit detached from the other novels in terms of style.
And on a sidenote, the word yakata refers to a mansion than 'just' a house, but the titular house in The Decagon House Murders isn't really a mansion (in the grand, impressive building-meaning of the word), but an annex building of the actual, main mansion. This is why I first used the word house instead of mansion as a translation for jukkakukan (decagon house): I just sticked with the word in other reviews to be consistent, although subsequent houses can all safely be called mansions.
As the titles of the books suggest, each book is set around a different creation by Nakamura Seiji. There are two major 'types' of house, which tie in with the creative writing process behind the books. Writer Ayatsuji Yukito sometimes comes up with an interesting-sounding house, after which he thinks of a plot to set in that house (i.e. Bikkurikan no Satsujin). Other times, he comes up with a plot, after which he creates a house to support that trick/plot/story (i.e. Tokeikan no Satsujin). In general, the latter practice leads to houses which are integral to a certain trick in the book, as the houses are created especially to facilitate execution of the plot.
The most important characteristic of the series is of course the plot device of the mansions as a setting. This is highly influenced by S.S. Van Dine's The Greene Murder Case and especially Oguri Mushitarou's Kokushikan Satsujin Jiken (1934), which also features a dark house brimming with secrets and surprises. The horror-like style can be felt distinctly throughout the stories (Ayatsuji Yukito also writes horror conveniently) and it results in each of the houses becoming something like a living entity in each narrative, not unlike the House of Usher. A great number of the novels are so-called closed circle
mysteries: in these novels everybody is confined to the titular mansion,
with a murderer among them (a bit like Scooby-Doo. A little bit). These mansions also all feature secret passages, hidden rooms and other surprises that would make Knox go utterly mad. One might think for a second that such elements would make a detective story unfair, but because these secret passages are taken for granted in Nakamura Seiji's houses, it's never unfair. Everyone knows they exist, and the way writer Ayatsuji utilizes them is absolutely fair to the reader (for example, the existence of a secret passage itself might come out of nowhere, but not the question of who could have used the passage).
And for fans of the genre who like maps and stuff in their novels, there's always a neat, detailed map of each mansion in every novel!
There is another major characteristic to the series, but this includes major spoilers for the novels, so I'll hide the next part. SPOILER ALERT!! I REFER SPECIFICALLY TO THE DECAGON HOUSE MURDERS AND THE WATER WHEEL HOUSE MURDERS. READ AT YOUR OWN RISK (SELECT TO READ):
Most of the novels feature a narrative trick to be springed upon the reader, usually executed through a dual narrative structure. The Decagon House Murders for example had the two narratives of island and main land, while the The Water Wheel House Murders had a past/present narrative. Ayatsuji's narrative tricks are usually accomplished by suggesting either a link between the two narratives, while in reality there isn't, or the other way around. The Decagon House Murders for example made it seem like the island narrative was a closed circle And Then There Were None scenario, while the main land narrative was about finding out the truth behind the events. However, one person from the main land narrative had in fact been traveling up and down the island, posing as another person there, having broken the closed circle. The Water Wheel House Murders made it seem like the narrators from the two past/present narratives were the same, even though there had been a switch. The other novels also feature such tricks (practically all have dual narratives), but the narrative trick isn't always crucial to the main story (sometimes it's just to give the story another surprise twist, but not particularly crucial to the murder-plot).
The Yakata series was originally planned to end with the fourth novel, The Puppet House Murders, but is now planned as a ten novel series, of which nine have been released at the moment.
Note: The novel The Kirigoe Mansion Murder Case is formally not a part of the series, but the book does open with "dedicated to another Nakamura Seiji" and similarly features a mysterious house as the scene of murders, suggesting that the Kirigoe Mansio might also be a creation by Nakamura Seiji.
Note 2: The Ayatsuji Yukito Murder Case is the novelization of a murder play inspired on the yakata series.