Appears in the story "The Case of Mariko and Kaori". Kaori is Mariko's childhood friend, though Mariko has been cold towards Kaori ever since she something went wrong when Mariko agreed to let Kaori confess to her crush in her stead. When she finds out about the mermaid's flesh myth from Haruko, Kaori captures a mermaid with the intent of apologizing to Mariko. Mariko eats the "G" mermaid's flesh but runs off soon after, and Kaori turns into a mermaid at dawn. Wracked with guilt, Mariko returns to the school the next night and meets the mermaid Kaori, who offers her a piece of her flesh — however, Mariko refuses it, choosing to turn into a mermaid to remain by Kaori's side. In a dialog between two unseen girls, it is implied that Kaori had romantic feelings for Mariko.