The kouda sisters in kamakura receive a letter informing them about their father's passing away. although yoshino and chika are not particularly attached to him, they decide to travel to yamagata for his funeral at sachi's request. during this trip, the sisters encounter suzu, their half-sister who has been living in yamagata.
Umimachi Diary won the Excellence Prize in the manga category at the 2007 Japan Media Arts Festival Awards, the Manga Taisho Award in 2013, and the 61st Shogakukan Award Manga in the general category in 2015. It was also nominated for the 1st Manga Taisho Award, for the 12th Tezuka Osamu Cultural Prize, and for the 13th Tezuka Osamu Cultural Prize.The series was adapted into a live action film by Hirokazu Kore Eda in 2015 (released under the title Our Little Sister in the West). The film competed at the 2015 Cannes Film Festival for the Palme dOr.