Hikari no Umi

Collection of five short stories revolving around mermaids and mermen.
Sayonara Spangles
Natsuki and Ec-chan are friends with a mermaid who dreams of growing legs. With the help of a spell book and Natsuki's crush, Mizuno-sempai, the girls hope to fulfill her dream; unfortunately, the plan brings some unwanted complications.
(Source: M-U)