Just the facts, please: Testuro Tamba (right) and Kensaku Morita on the trail of murder
There isn't really too much mystery, however. From the moment Tamba's detective notes the presence of celebrated composer/conductor Eiryo Waga (Go Kato) on board a train you know the musician will be part of the murder mystery, if not its solution. Matsumoto and Nomura keep things mysterious, however, by building mystery on top of mystery. By the second half of the picture the real mystery is: who is Eiryo Waga, exactly? He claims to be an orphan, his parents having died in a wartime bombing of Osaka. His girlfriend, whom he's gotten pregnant, blames his coldness and unwillingness to be a father to the baby, on that origin story. Whether Waga killed the old cop or not, he does have at least one death (or two) on his conscience after the spurned girl suffers a miscarriage and dies from the complications. But there's more to his story than the poor woman could have guessed, and the detectives have to piece Waga's history together before they can draw a line from him to the murdered policeman.
Orchestra conductors are so menacing looking, you can't help suspecting them.
Over the final third of the picture Tamba pieces together Waga's story, his report to his superiors providing a framing device for an extensive flashback showing that the composer has had three fathers. His biological dad Shokichi (Yoshi Kato; any relation to Go?) gets leprosy, rendering father and son (mom died long before) social outcasts. A maudlin montage illustrates their ordeal as beggars and scavengers until Ogata's policeman intervenes. After Shokichi is forcibly separated from his son and hospitalized, a concerned Ogata takes the boy in and raises him as his own until the kid runs away to Osaka to join his third family. Eiryo Waga has been twisted by injustice -- an epilogue notes that sufferers from Hansen's Disease are no longer ostracized as Shokichi was -- until he rejects all intimacy, sublimating it into his music. Ogata was probably tempting fate by prodding Waga into visiting the old man, who ironically is still alive in the film's present day. As Tamba deduces, Waga now can only communicate his feelings through his musical creations, the latest of which is portentously titled "Destiny." Waga strives to be a self-made man while eliminating any ties to his past, but you can't escape destiny, or at least you can't escape a dedicated detective.
The repressed past: Eiryo Waga begs alongside his afflicted biological father
and turns his back symbolically on his surrogate dad.
The big flashback is clearly heartfelt and may well have tugged at Japanese heartstrings, but coming at the climax of a realistically structured procedural it seems like a shocking throwback to the style and sensibility of silent melodrama. The film's problems with consistency of tone may be a matter of cultural perception, however. I won't back down, however, from criticizing Castle of Sand's pretension that "Destiny" (actually composed by Mitsuaki Kanno and/or Kosuke Sugano) is anything like a brilliant piece of modern classical music. As a rule, beware whenever film composers pass off their work within a film as a serious composition. Movie soundtracks are often brilliant on their own terms but modern classical music is a profoundly different animal and a failure to recognize the difference is sometimes embarrassing to the film composer. But since Castle of Sand is not a musical or really about music you can forgive this miscue. Likewise, Nomura may go over the top with sentimentality in relating Waga's sad backstory, but he also makes the case that this tale of woe is essential to understanding what happened and cracking the mystery. If he's gotten you committed to the mystery in the first half of the film you should be able to stand his emotional excesses in the second half and respect Castle of Sand as both a murder mystery and a kind of modern tragedy.