When the Rocket Girls accidentally land in the yard 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 Solomon Space Association. Yukari and Akane are then given the biggest Rocket Girl mission yet: a voyage to the edge of the solar system and the minor planet of Pluto to save a NASA probe.