Kohinata Ayumi is about to go on a date with her boyfriend Shiro, but then she gets a mysterious call from one of her classmates! Suddenly, she wakes up in someone else's body!?

Choa is a mermaid who can't swim! Discouraged, she trades the ocean for a pair of human legs. But when the star of the high school swim team finds out her secret, he offers her the chance to prove her family...