When Tokiko's parents break up, 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 Yosuke, another outsider, wants to be friends.

But then strange memories start to surface.

Swimming in the ocean...

Drowning...

Getting saved by...

...a merman?

Yosuke denies the presence of merfolk, yet the townspeople hold a festival to honor them every year. Can Tokiko solve the mystery of what is real and what is fantasy...?