Summary of the story of Umi-chan: Umi-chan works as the number one maid at a maid cafe in Akihabara, Tokyo. After being suddenly given a week off by the manager, Umi-chan returns to her family's seaside restaurant for the first time in three years, only to find a rundown exterior and a sign saying "Closed." In order to protect the words of her beloved grandfather, Tobio, Umi-chan decides to reopen the restaurant as a maid cafe. While involving Umi-chan's grandmother Yoko and her younger sister Nagi, Umi-chan overcomes various difficulties to make the maid cafe a success, and in the process, she begins to remember how much she cares for the sea in this heartwarming comedy.