Appears in the story "The Case of Hidemi and Nanae", which takes place in 1986. Hidemi is a high school student who is often the subject of gossip due to her standoffish attitude. Although she pushes away her childhood friend, Taizou, whenever he expresses concern for her, she is secretly happy about it and becomes upset when she sees him with another girl. Contrary to her appearance, Hidemi is quite strong and good at fighting. Hidemi's suspicions about Nanae's abnormal interest in her are confirmed when the latter involves her in the ritual with the goal of turning Hidemi into a mermaid and consuming her flesh in order to get Hidemi's crush, Taizou, to fall in love with Nanae instead. Both manage to escape the confrontation, with Hidemi slashing Nanae's face in self defense. After these events, another student named Hayashi reappears just as suddenly as she'd disappeared, and Hidemi suspects that she was involved in a mermaid hunt — which is confirmed when a male student goes missing around the same time, and one night she spots Nanae taking Hayashi away in a taxi and follows them to the seashore. There, she finds Nanae chanting a variant of the words to the ritual which results in Hayashi turning into a real mermaid, with a fish bottom half. A horrified Hidemi witnesses Nanae consuming Hayashi's flesh, and pieces together many years later that a true mermaid's flesh granted eternal youth and rapid healing, as evidenced by Nanae looking just as youthful decades later and no longer sporting a scar on her face. Hidemi goes on to marry Taizou and give birth to Shinobu.