This world is made of a single massive castle. The important people live in the upper layers, and the poor live in the lower layers—— In such a closed world, Yao and Fuu run a "Yorozuya" (general store). Yao never stopped believing that there is another world outside the castle, and one day, a lonely girl he meets shows him a landscape that seems to be from outside the castle——!? An adventure story woven by a boy who dreams of the world outside and a girl left behind by the world!