A 1961 novel by Japanese mystery writer Seicho Matsumoto. The eponymous police officer begins investigating the murder of an unknown man found on the railroad tracks, and starting with almost no clues, he travels around Japan to make sense of the crime and find the killer. The novel also centers on a group of trendy young artists called the Nouveau Circle, who seem to have some connection to the murder.
Adapted into a Japanese film called Castle of Sand.
Contains examples of:
- Alliterative Title: All three words of the translated title, start with "I".
- Asshole Victim: Deliberately inverted. The murder victim turns out to have been a kind, philanthropic man loved by all who knew him. Thus, the mystery is both a question of "who killed him" and "why would anyone kill him".
- Conveniently Unverifiable Cover Story: It turns out that the name/identity by which the murder was known was not his real one, but rather the result of taking advantage of one of these. Specifically, his supposed parents were a couple killed in a bombing raid in Osaka at the very end of World War II, and he falsified records so that he would seem to be their son.
- Determinator: Imanishi essentially becomes completely devoted to pursuing one case and starts with little to no evidence, but eventually finds enough to catch the killer.
- Never One Murder: Played straight, but except for the one that starts the plot going, all deaths seem to be from accidents or natural causes.
- Tohoku Regional Accent: Plays a big part in the plot, as those who saw the victim before his death recollected the distinctive Zu Zu sound, and Imanishi tries to find the victim's identity based on that accent.