The story is set in 1963 in Yokohama.
Kokuriko ( from coquelicot, French for Papaver rhoeas )
Manor sits on a hill overlooking the harbour. A 16 year-old girl, Umi,
lives in that house. Every morning she raises a signal flag facing the
sea. The flag means "I pray for safe voyages". A 17 year-old boy, Shun,
always sees this flag from the sea as he rides a tugboat to school.
In preparation for next year's Tokyo Olympics, people are destroying
the old and believing only in the magnificence of the new. In that time,
at a high school in Yokohama, a small struggle occurred. The building
of the Culture Club, nicknamed Quartier Latin, is old but full of
history and memories. Should it be destroyed or preserved? In the middle
of this, Umi and Shun meet. Shun appeals to the students who want to
protect the building. Umi suggests a big clean up of the building to
show its good parts.
Gradually the pair are drawn to each other but they are faced with a
sudden trial. They may be siblings. Even so, they keep going without
running from reality. Then, in the middle of the battle and the
aftermath, they come to know how their parents met, loved and lived.