Meiji Era, an increasingly populated port city.

Mari, 16 years old, is a half-Japanese girl with beautiful wavy blond hair and big blue eyes like her father. Her appearance is considered heresy and she is constantly discriminated against. To avoid this, she stays hidden most of the time.

She observes from a distance a student who often lacks in inspiration. However, this student, who's named Shintaro and is the son of a celebrity, meets the girl one day and tells her that she looks like a mermaid.

From that day on, Mari plunges into a world beyond her status and origin.