The Port of Yokohama, Japan, 1963. With the country gearing up to host the upcoming 1964 Tokyo Olympics, shy and industrious high-school student Umi starts her day by raising signal flags to greet passing ships from up on Coquelicot Manor. Despite being a wallflower at school, Umi inadvertently catches the eye of Shun, the self-confident school newspaper president, who has been harbouring a secret crush on her for quite some time. As fate would have it, Shun introduces Umi to the "Latin Quarter", a rundown mansion that doubles as a vibrant clubhouse for students interested in drama, chemistry, philosophy, journalism, and more. Together, they embark on a challenging mission to save the beloved structure from the wrecking ball, even as school administrators insist on demolishing the old building. Against the backdrop of a rapidly modernising Japan, two young dreamers work together to preserve the cherished hangout, unaware they are on the path of self-discovery and newfound love.