Akari Shiroma is a high school student from Urasoe City, Okinawa Prefecture, who initially shows little interest in local history. Her life changes dramatically when she accidentally travels back in time to the Ryukyu Kingdom era while walking on flat grassland, leading to an encounter with its historical ruler, King Satto. The story explores her interactions with King Satto and his court, including figures like Masato, Yousai, and Daijin, as she navigates the cultural and historical differences between modern Okinawa and the ancient kingdom, serving as a bridge between these timelines.

In the sequel "Ryuukyuu Timeline 2: Tedako no Machi Tanbou," Akari returns alongside two other high school girls, Sarah Arakaki and Tsubasa Kinjou. Together, they embark on explorations related to the "City of the Tedako," interacting once more with King Satto and other historical figures such as Gihon-ou, Shisha, and Eiso-ou. This continuation expands her role in uncovering historical mysteries across different eras of the Ryukyu Kingdom.