Umi is a high school student living with her family in Yokohama in 1963. From their home on a hill overlooking the ocean, she raises two flags every morning towards the bay to convey a message. When a poem about the flags is published in the school newspaper, Umi wonders if the bold editor, Shun, is the author. As they team up to save their school's historic clubhouse, Umi and Shun uncover a hidden truth about their past that changes the course of their blossoming romance. Against the backdrop of Japan's evolving blend of tradition and modernity, their story is one of companionship, love, and ambition.