The Case
Conan along with Heiji, Ran, and Kogoro visit the Isle of マーメイド looking for Saori Kadowaki, who had sent a letter to Heiji asking them to save her from being killed によって a mermaid. In secret Heiji confines to Conan that the letter was meant for Shinichi despite being send to Heiji's address. But when they try to look for Saori she has been reported missing. They decided to talk with Saori's childhood friend Kimie, who is the elder's great-granddaughter. Rokuro Fukuyama the fisherman is Toshimi's fiancé. Those two along with Naoko, a ショップ clerk, are also childhood フレンズ with Saori. They don't seem concerned over Saori's disappearance, but that's because Saori often left home, when she had argued with her father. Every 年 on this island a festival is held where three people win the Dugong ARROW/アロー that is 発言しました to wield immortality to its carrier. Saori won one last year, but have ロスト it and had since been paranoid about being curse によって マーメイド up until her disappearance. Kimie offer Ran and Kazuha each a ticket to the lottery, since a couple called off, and promise to take them to Saori's house after the festival. During the festival Kazuha wins an arrow, which she receives along with Naoko and Saori's father Benzo. The festival is brought to a disastrous end when one of the winners is found dead hanging down the waterfall.
The deduction
Conan and Heiji investigate the area and history of マーメイド Grave, a forest on mermaid island. They learn that an elder who is over 130 years old is a holder of the ARROW/アロー and the head of the festival. Three years 前 a warehouse got burned down and a half body was discovered missing its legs. The police from the coast 発言しました that the body was of a middle age woman, and concluded that it might have been a tourist, who snuck into the warehouse to look for a dugong ARROW/アロー and accidently started the fire. The deceased was never identified. But rumors had been going around that it was a body of a mermaid. The 年 after the incident, the BONES（ボーンズ）-骨は語る- were buried on the island, but later moved into the forest on orders from the Elder due to grave robbers who had stolen BONES（ボーンズ）-骨は語る- from the grave. In myth it was believed that BONES（ボーンズ）-骨は語る- of a mermaid grant long life. It was that incident that made the Elder famous around the country. Naoko suggest that Toshimi had been looking for the grave, and Kimie confirms that Toshimi often spoke of it. While investigating two もっと見る murders occur. First Naoko being strangled and her ARROW/アロー is missing. The only connection between the three women, beside being childhood friends, is that they all three believed in the power of the arrow, and that the Elder was immortal. Heiji and Conan decides to take a look at the book with the names and numbers for those who anticipated in the festival's lottery, but the most 最近 one is missing. While Kimie goes out to 検索 for it. Heiji and Conan takes a look at the old ones. Conan finds a name, Shihi Miyano, and remembers that it was Haibara's real name, but doubts that's her. Then Kimie gets burned in the warehouse near the shrine. After the corpse's identity is determent によって dental records, Rokuro breaks down crying and the 'Elder' takes to her ベッド muttering about seeing young life dying, while she still lives. The group splits up, Heiji and Kazuha goes out searching for Benzo, while Rokuro takes the rest to Saori's house, so Ran can see a picture of Saori and determent if she was the woman, she and Kazuha saw. After searching a bag for travel in the house Conan realizes that something is missing. He reveals to Heiji he knows who the murderer is, relay his theory, and asks him to meet up later, but later Heiji and Kazuha fall off a cliff after they discovered the much-talked-about grave. At the grave Heiji sees that someone has visited it recently and begins to wonder if Conan's solution was correct.
The Resolution
Heiji saves Kazuha and they're still having trouble. While everyone is waiting for the deduction of Sleeping Kogoro, Ran arrives with Lady Mikoto, to the chock of the island's elder citizens. Sleeping Kogoro is now going to present a deduction.