During a family trip Mira Konohata befriends Ao Manaka, who she believes is a boy, and makes a childhood promise with the stargazing Ao to someday discover an asteroid together. After she enters high school Mira then joins the Earth Science Club, which is a merger of the school's now abolished astronomy club and the geology club, and discovers that one of its female members is her friend Ao. Now reunited Mira and Ao, who renew their friendship, alongside their fellow female members will take part in various astronomical and geological activities during which the two girls will try to fulfill Mira’s promise.
