Heiji and Kogoro are invited to Okinawa to solve the case of a body that was found on Onikame (???, lit. Demon Turtle) island alongside a mysterious carved message by the body. The deduction battle between the two shall be televised in order to boast the declining tourism of Okinawa. Heiji, Conan, Ran, and Kazuha head to the island to investigate and are accompanied by four TV station employees. They find the mysterious message as "The sleeping place of a princess shall be K? and not Otu" where K? and Otu could stand for multiple meanings. When Yoshie Taira is found strangled, the dying message "I am a Servitor of Goosoh", Heiji realizes she must have found something and dives into the water only to find an anchor. When they prepare to head back, they find out the captain left with the boat, stranding them on the Onikame. They decide to wait in an abandoned house until a rescue boat arrives.