The mystery/police investigation in this novel is very good, the solution is clever, with one trick in particular that I found excellent, and the reader is given all the elements they need to participate.
The mystery mostly resolves around train timetables, and unfortunately, I was too lazy to really try to work out a solution by myself. While this might be the main reason why I did not enjoy this novel as much as expected, there are also other elements that prevented me from feeling engrossed in the story.
First of all, I found that the novel throws several leads at us but does not really commit to any of them. The first one, which looks like it is going to play an important role in the story, is the trade union and negotiations between the company and the workers. Then we have religion playing a role with employees asking for freedom of religion (this took me a while to understand, because I was not aware that a company could impose a religion on its employees!). This makes for a complex and interesting setting for a murder story, but the story then moves on to other topics and we never really come back to this interesting setting.
Similar thing happens with the characters. The story opens with two women, one of which will clearly play a role in the story. We leave her in a difficult situation, but we won’t see her again until much later in the novel. Most of the novel is told from the point of view of the police detectives, but at some point, we follow other characters for a short sequence, and go back to following detectives. Even the detectives are split in two groups, and this did not really work for me (I prefer following the same duo of detectives from beginning to end, rather than follow one duo and then abruptly switch to another).
I also felt that the real purpose of a lot of scenes was the social aspect of what was described rather than the investigation itself, which sometimes felt a bit slow for a mystery novel. It often felt like the author just wanted to describe something, be it a place, a movement (like the labour movement), a professional area, etc. for the sake of the description rather than to advance the plot. The novel explores a lot of different social classes, and some passages felt like describing all of this was the real purpose of the book, and the investigation just a means to do it. So sometimes, we will have a long description of a certain place and little useful information relative to the case.
This makes for a good social novel, and it is great if you want to have a picture of the time, but it also felt frustrating to go through so many steps and descriptions just to confirm that what a certain character had said was true, or something of the sort.
I do think that this is a good detective novel overall, I just did not enjoy reading it very much. The end was good though, and I don’t regret reading it nor was I tempted to DNF it. However, I did not make me want to read the other prize winner of the same year (same author, same series), and I doubt that I will continue the Onitsura series.