A jogger discovers a male corpse wrapped in blue tarpaulin on the Tokyo embankment of the Edogawa. Someone has stripped the man's body, beaten his face until unrecognizable, burned off his fingerprints, and set fire to his clothes. Marks around the neck mean someone strangled the man but how did the body get to the river? What is the meaning of the bicycle with punctured tires? Who is this dead man?
So, a straightforward police procedural and whodunit? Not really, because we know who the dead man is, we have already witnessed the crime, we know who helps dispose of the body; we know the motive, the scene, the killers, and the murder weapon. At least we think we do. The police think they know who did it. Even the killers think they know who murdered the man. They did, didn't they?
The mystery plays out like a reverse chess game — we know all the moves, we know the way to checkmate, but how from an endgame do we get all the pieces back into their original positions?