Saori Kadowaki (Michiru Wada) was a villainess from "And Then There Were No Mermaids", episodes 9.09, 9.10, and 9.11 of Case Closed (airdates January 29, February 5 and 12, 2001). She lived on an island known as "The Isle of Mermaids" and was the daughter of fisherman Benzo Kadowaki. Her mother died five years prior on the sea along with her friend Kimie's father and their friend Rokuro's parents.
Saori's letter asking for help in keeping a mermaid from killing her was sent to Heiji Hattori, who came to the island along with his girlfriend Kazuha Toyama, Kogoro and Ran Mouri, and Conan Edogawa. Once there, however, they learned that Saori had mysteriously disappeared, though this was originally dismissed by her friends (Kimie Shimabukuro, Toshimi Ebihara, and Rokuro Fukuyama) as her habit of running away after having an argument with her father and that her letter to Heiji was inspired by her losing the Dugong Arrow she'd gotten at the town's annual festival the previous year.
But later on, after Toshimi and Naoko Kuroe (another friend of Saori's) were found dead, the truth of Saori's disappearance was discovered by Conan: she had been murdered by Kimie, who subsequently used Saori's body and dental records to fake her own death to avoid suspicion. Kimie had also been posing as the island's "Elder", her great-grandmother, for three years; another ruse exposed by Conan. Following Conan's summation, Kimie unmasked herself and revealed her reason for killing Saori and her other friends: revenge for the death of her mother, who had died three years prior in a fire that broke out in their shrine's warehouse and who had passed the tradition of being the island's "Elder" to Kimie before she died (having been posing as her grandmother herself to serve as the town's Elder).
Kimie revealed that that year, Saori (along with Toshimi and Naoko) were angry at not receiving a Dugong Arrow at the island's annual festival, and decided to get revenge by setting the warehouse on fire with Kimie's mother disguised as the Elder inside it; also doing so as a "test" for her rumored immortality. They had no knowledge of the ruse, so it' s fair to assume that when Kimie secretly took over the role as Elder and her mother's corpse was found with it's legs missing, Saori and her two co-conspirators jumped to the conclusion that the Elder was immortal having survive the fire and that the found skelenton was of a mermaid hidden in the warehouse. In the present day, Kimie learned the truth about her mother's death when Saori lost the arrow she'd won in the previous year's festival and asked Kimie for a new one, accidentally revealing in the process how she'd killed her mother due to her delusional belief that the "Elder" had survived the fire. Enraged at her friends' callous actions and Saori's lack of remorse, Kimie killed Saori and stored her body in the warehouse later on to use in her plot to kill Toshimi and Naoko.
Sadly enough the dissapearance of her arrow which started the whole case turned out to be a theft committed by Saori's father Benzo who sold it for a million yen to a couple. He claimed that as Saori's father he had right to sell the arrow.