From Up on Poppy Hill

Umi Matsuzaka, the eldest sibling in a close-knit family of five, raises a pair of signal flags everyday at her seaside house in Yokohama Bay without fail in anticipation of the return of her father, who went missing in action during the Korean War. In school, Umi finds herself involved in a student movement seeking to prevent the demolition of an old club house. In the process, she falls in love with the newspaper club member Shun Kazama, only to find out that they might be related by blood.

Synopsis from Anime News Network