Everyone besides Tokiko denies the existence of merpeople, and yet the town holds a secret annual festival to honor them. Can she solve the mystery of what is real and what is fantasy...?

When Tokiko's parents' marriage falls apart, she and her father move from the bustling city to a sleepy coastal town to live with her grandmother. Starting sixth grade in a new school where everyone has known each other their whole lives isn't easy. Things start to look up when local boy Narumi, another outsider of sorts, wants to be friends.

But then strange memories start to surface.

Swimming in the ocean...

Drowning...

Getting saved by...

...a merman?