Three schoolgirls are conscripted into the Solomon Space Agency to become the youngest ever astronauts of Japan.

Adventurous Yukari Morita embarks on a quest to find her birth father Hiroshi, an astronaut who abandoned her mother on his wedding night. She tracks him down in the Solomon Islands, at the SSA (Solomon Space Agency). She meets the base director, Nasuda Isao, who is in a predicament: the SSA is in danger of closing down due to continuous failures at launching full-size spacecraft into orbit. The only alternative for the base is to utilize a small spacecraft, but the problem is that it's much too small for adults to ride. Isao offers Yukari a deal: he will help her find Hiroshi, and in return she must take a job at the base. Yukari starts out with the simple job of pressing buttons... but soon Isao talks her and her friends, her stepsister Matsuri and the shy geek Akane Miura, into becoming Japan's youngest ever astronauts!—Tenchi