CashHarbor, with an overhead planet as the background where the weather is very bad and terrific, many sea monsters exist and lands are distributed sporadically, there the inhabitants are divided into two classes of fliers and islanders; for fliers, the hereditary custom is passed generation by generation, trespassing is forbidden. The novel tells that an island girl tries every effort throughout her life to break through social barriers in order to realize the dream of being a flier, and a social transformation is triggered because of this; her mind is becoming increasingly mature due to the unimaginable consequences brought by her own actions. Finally, although she losses the flying ability in an accident, she becomes a well respected great flier through her own behaviors.