Yokohama, 1963. Umi is a high school student living in her family home overlooking the sea. Every morning she hoists two signal flags towards the bay, sending a message to the horizon.
A poem about the flags is published in the school newspaper. Maybe it is written by Shun, the daring newspaper editor who has drawn Umi’s attention. Umi and Shun join the campaign to save their school’s old clubhouse, and their budding relationship takes an unexpected turn when they discover a secret surrounding their past. In a Japan caught between tradition and modernisation, Umi and Shun’s story is one of friendship, love and hope.