Nanokakan no minoshirokin, Seven Days' Ransom, 1986) is an impossible crime puzzle by 岡嶋二人 (OKAJIMA Futari). A little late, I've added "impossible crime" to the blog's post labels. Japanese detective stories often use "locked room" to describe impossible crimes which don't involve a locked room, or sometimes even a room.
CHIKAISHI Chiaki (近石千秋) and TSUKISHIRO Younosuke (槻代要之助) are a musical duo. Chiaki writes the lyrics, Younosuke sets them to music, then Chiaki sings the songs accompanied by Younosuke on piano. The two of them are in their mid to late twenties, hoping to get a start in the music business. When we meet them, the two are friends, who have somehow missed the point where they might have become lovers. Chiaki is also the daughter of a senior policeman. It's through her eyes that we see the story.
The novel starts with the video of a ransom demand. An acquaintance, TOBA Sumako (鳥羽須磨子) has asked Chiaki's advice after receiving the video, which shows her stepson, TOBA Kunihiko (鳥羽国彦), and her brother, TAKENAKA Kazumi (竹中和巳), tied up. In the video Takenaka is reading a ransom note to the camera, with the kidnappers' demands. Rejecting Chiaki's urgings to contact the police, Sumako sets off with the money. With no time to telephone and not knowing where Sumako has been told to go, Chiaki and Younosuke set off chasing after her Porsche in Younosuke's Sunny. Even though a kidnapping is a really unpleasant crime, the tone here is actually almost light hearted. Sumako drives to one café after another, evidently picking up instructions from the kidnappers. By quick thinking, Chiaki and Younosuke manage to discover the place where the next instruction is and inform the police. When Sumako goes to the final destination, an uninhabited island in a lake, connected to the mainland only by a long bridge, the police are waiting. To avoid being spotted by the kidnapper, they have kept their distance; but there are boats on the lake and policemen watching from cover on the mainland. A little after Sumako reaches the island, the police hear a shot and rush there from the lake and from the mainland. Sumako has been shot, the killer is nowhere to be seen. The gun and the ransom money have gone too.
This is obviously a fairly open impossible crime. Escape via the lake, on the water or under the surface, cannot be absolutely ruled out, although the police seem confident that that would be impossible. Other possibilities are likely to occur to readers familiar with the form. But whatever we may have been speculating gets put aside about half way through, when a discovery removes this impossibility and replaces it with a new kind of impossibility.
The puzzle has an odd form: for most of the story, all our suspects are off scene, since everyone connected with the case is either dead or missing. The lighthearted tone also evaporates fairly quickly. Chiaki starts looking like she might be a typical figure of Japanese popular literature, the attractive young woman who always gets what she wants by self confidence or wheedling or family connexions. But the depiction does not go very far in the "charming but infuriating" direction and treats her more seriously as a young woman deciding what she wants in life. The depiction of the two central characters is perhaps a little weak. Their profession is potentially interesting, but has no relation to the story; and we see very little of it. One could criticise the puzzle on the grounds that some bits are overclued and some underclued. It also demands that the police miss a few things, some understandably, some less so. The two main tricks are good enough for a novella, perhaps not quite for a full novel; but Okajima Futari are skilled at involving the story in interesting episodes.
I nearly left out the illustration here. I like that Japan keeps cover artists in business; and some are lovely. This isn't one of those. I put the picture size to "small".