Yukari Morita is a high school girl on a quest to find her missing father. While searching for him on the Solomon Islands, she receives the offer of a lifetime-she'll get the help she needs to find her father, and all she need do in return is become the world's youngest, lightest astronaut. Yukari and her teen friends, all petite, are the perfect crew and cargo for the Solomon Space Association's launches, or will be once they complete their rigorous and sometimes dangerous training.