Long ago, a rampant fog divided the world, covering the seas and skies and cutting people off from one another. Generations passed. People built small towns and stopped wondering about what lay beyond them. The protagonist is a girl who lives in Soi — a town where wildflowers grow freely — and has not inherited that resignation. For her summer vacation research assignment, she decides to investigate what lies outside the town. The mist is thicker out there, and monsters have appeared. With her childhood friends Tsukishiro and Shuka at her side, she steps past the town's edge. Neither of them knows what is waiting.