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. She navigates the cultural and historical differences between modern Okinawa and the ancient kingdom, serving as a bridge between these timelines. In a continuation, Akari returns alongside two other high school girls, Sarah Arakaki and Tsubasa Kinjou, and 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.