Marika Katou, a third-year student at Hakuho Girls' Academy, has a Letter of Marque and is a bonafide space pirate. Marika's days are filled with studying, leading her school's space boat club, working part-time at Cafe Lamp, and captaining the space pirate ship Bentenmaru. Marika gets a job robbing a high-class passenger ship one day, and she sees on the passenger list Kanata Mugen, a youngster with a "galaxy pass." Thus begins an adventure involving a hyperspace race between pirates and a small boy.