Mermaid/Synopsis

Hanako-san of the Toilet
The Mermaid appears at the end of the chapter to claim Nene, who had swallowed her scale, as her new servant. She was taken by surprise by Hanako, who she underestimated due to his age as a supernatural, and was wounded by his attack. She retreated from the scene, cursing the School Mystery.

The Little Mermaid
The Mermaid was briefly mentioned by her Mermaid Servant. It is revealed that is very kind, despite her appearances.