Far in the future, where interstellar travel is considered commonplace, high school student Marika Katou balances her duties in the space yacht club and her job as a restaurant waitress. Following a chance encounter with a peculiar pair of customers, Marika meets them again and learns that her absent father has passed away.

During his life, he was known as the legendary pirate "Gonzaemon." He has left behind his infamous ship Bentenmaru and its crew exclusively for Marika to inherit. With one of the few remaining Letters of Marque that permit legal piracy, Marika must choose whether to stay as a regular student or take up a second life as a high-octane space pirate.

As Marika ponders her decision, the delicate situation attracts the eyes of various government agencies and the mysterious transfer student Chiaki Kurihara, all eager to see if the upcoming captain lives up to her father's reputation. If the crew of the Bentenmaru want to maintain their status, they will need to set sail into the vast expanse of space and once again become a name to be feared.