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The award-winning author Imatake Satoru was killed in his hotel room on the night of the Tenkaichi Festival. The murderer: his long-time friend and colleague, Sasai Norikazu. He shot the unsuspecting victim point-blank and left the scene immediately after.
Imatake was found dead with traces of toothpaste on his mouth and a toothbrush lying on the ground near him. His wallet was empty and the room was ransacked.
Sasai was the primary suspect but he had an alibi. In his disposable camera were pictures of him at the festival; and the festival events coincided with the time the killing took place.
Conan, aiding Inspector Sango Yokomizo through Inspector Kogoro Mouri, proved that it wasn't just a simple case of robbery and that Sasai was indeed the killer.
Imatake was murdered while brushing his teeth, an act done without inhibitions in front of people whom a person is very familiar with. The bad condition of the room was evidence enough that the robbery was a setup, for the killer fled the scene right away after the gun was fired. And the pictures seemingly taken that night, thus proving Sasai's innocence, were actually from the the past Tenkaichi festival, as his wrist was captured without his current watch tan line.
Over a year ago, Sasai felt ridiculed when the more well-known writer Imatake's work was chosen to be published over his at the last minute. Imatake apparently became famous when he won an award for a book that they co-wrote, while Sasai wasn't credited for it.
Sasai planned the murder, so that he could take Imatake's place as top writer in the literary world.
See also