A mermaid who can't swim? It's ridiculous, but here you are, living as a human, staring at the water after your school's swimming competition at the edge of the pool.

"Oh! Hey! What are you doing here?"

Tanjiro, your classmate and swimmer, surprised you, causing you to fall into the pool and transform as you sank, he jumped into the water to help you and accidentally discovered you... You can't escape, you can't swim, what will you do?