During a war of independance, a planet issued letters of marque, and 'legal pirates' were a fact. Now the war is over, but the pirates persist. When one dies, their children can inherit the letter, giving rise to some sort of piracy dynasty. Sixteen year old Marika is the daughter of a pirate, a father she never knew. But now he died, and she inherits his letter of marque, making her the rightful captain of the pirate ship Bentenmaru!
Marika takes her time making a decision, but during a 'practice cruise' with her girl's school yacht club (which means space yacht, of course) she gets a taste of what it means to stage a counter-attack when you're attacked in space. This makes her decide to take on the job of pirate captain, in addition to her school work. But being a pirate often means staging a show of piracy on a space cruise ship, funded by the insurance company!
There are plenty of tense moments too, though, where Marika needs all of her smarts to get everything to a good end. There are quite a few ship-to-ship battles in the series, but instead of the adrenaline-powered fights of most mecha series, the outcome of the battles are determined by planning beforehand, cyber warfare, radar jamming and smart manoevering -- an aspect I find I really liked. (It's also in Starship Operators, which I liked as well for that very reason.)
Marika has a lot of 'agency'. She makes the decisions that she makes based on trust (in her crew), her intuition and intelligence. Her sometimes unorthodox way of seeing things makes her quite an effective pirate. She is not the willless object of the plots of others, but actively steers her environment to a positive outcome. We need more anime heroines like Marika, frankly. Most of the rest of the characters are interesting as well, but we don't see too much character development in the supporting cast.
There's just one thing: I do wonder why they wear skirts in zero-G. I don't think it would be very practical, and it must be hard to keep decent while ascending or descending the central shaft in a spaceship while wearing a skirt...
The writing of the series is not that good, though. In between the various story arcs, there are episodes that are just not that interesting: seeing Marika clean up the Bentenmaru is just not that inspiring. But during the multi-episode story arcs, things get really interesting and the pacing is very good. Visually, the series is quite nice, especially the spaceship CGI. The scene with the dinghy race when all the craft drop at the same time is eyepopping good. The voice acting is good, but I didn't really care much for the music.
All in all, we had quite a good time watching this series. I'll give it an 8.