When the Rocket Girls accidentally splash down in the pond of Yukari Morita's old school, it looks as though their experiment is ruined. Luckily, the geeky Akane is there to save the day. Fitting the profile--she's intelligent, enthusiastic, and petite--Akane is soon recruited by the Solomon Space Association. Yukari and Akane are then given the biggest Rocket Girl mission yet: to do what NASA astronauts cannot and save a probe headed to the minor planet Pluto and the very edge of the solar system.