The main character. Marika starts off the story as a schoolgirl who participates in her school's space yacht club and works part-time at a local Maid Cafe. It soon turns out that she is actually the only daughter of Gonzaemon Kato, captain of the pirate ship Bentenmaru, and therefore the only person who can take his place (legally). While she's reluctant to take on the role, she does display natural talent for the job and accepts becoming Captain of the Bentenmaru. She also captains Odette II as Yacht Club's President after Jenny and Linn graduate.
Ace Pilot: Marika's first scene shows her piloting a "dinghy" (a small one-person space ship) from space to a landing on the ground with considerable skill (although it's actually a simulator).
Introduced as just the New Transfer Student to Marika's class, Chiaki turns out to be aware of Marika's parentage, and display similar skills in piloting a space ship. It is later revealed that she's actually the daughter of the captain of the pirate ship Barbaroosa.
Nerds Are Sexy: (Male) pirate EW officers all swoon about her when she is in her nerd getup. Lampshaded when Marika wonders why they didn't prefer her "outside clothes", and Coorie's answer that EW officers spend too much time "watching the truth" to worry about appearances.
Damsel out of Distress: The rescue attempt is rendered moot when she takes a chance to escape by shooting her way to an electronic warfare/recon fighter with a pistol she had hidden under her wedding dress.
Ojou: Heir to the Dolittle Space Shipping conglomerate.
Precision F-Strike/Sophisticated as Hell: Her response to Lightning 11's demand for the Odette II's immediate surrender was "Bakame!" which is roughly equivalent to saying "You stupid son of a bitch!" in English, Crunchyroll subtitled it as "Nuts!". Either way it's not language you'd normally hear from an Ojou
Put on a Bus: Jenny has graduated from Hakuoh Academy by Sailing 12. (But she comes back during the Hakuoh Pirates arc.)
Silk Hiding Steel: A pistol to be precise and the silk was her wedding dress. It's a visual metaphor for her personality.
In episode 20 she dodges out of danger easily when one of the other girls loses control of her yacht in the simulator... which Kane had set to replicate the "great red spot" on Jupiter which is home to the strongest winds in the solar system.
In episode 21, after her dinghy's electronics have been knocked out, Ai has no navigation systems. What does she do? Open the hatch and proceed to stellar navigate by sight, without even a sextant.
Shrinking Violet: Appears as this at first, but is slowly starting to come out of her shell.
Hakuoh Academy Space Yacht Club
A club at Hakuoh Academy which Marika is a part of. Its activities include dinghy simulations and practice cruises on its training vessel, the Odette II. Its members have been involved in the Bentenmaru's affairs a few times after learning of Marika's pirate heritage.
Colour-Coded for Your Convenience: The hoodies the members wear are colour-coded to their school year, cycling between pink, green and blue. Gruier and Grunhilde have black ones.
Voiced by: Atsushi Ono (Japanese), David Wald (English)
The Grand Chamberlain of the Serenity Privy Council.
Badass Grandpa: In the manga, he has a brief fight with Schnitzer and easily holds his own.
Really 700 Years Old: Not quite so much, but he is quite a bit older than he looks, and he looks to be in his eighties. Explained in the novel by him being a genetically engineered, extremely long-live "Methuselah".
Retired Badass: When the show begins, she's working as an air traffic controller, having retired a long time ago from piracy. In the Grand Cross arc, she joins Ironbeard's crew, and proves she still has her old skills.
Reasonable Authority Figure: Marika was afraid to talk to the insurance agent at first due to Ririka's tale of Ham-to-Ham Combat she did with him. Turns out Show replaced that guy a few years earlier, and understood that the previous guy's method of doing things wasn't always the best. He actually does quite a bit to help Marika out during the series, whether its providing information, or pulling strings to let her pirate with a "back up" crew when the main crew is sick and quarantined.
Chiaki's father and captain of the pirate ship Barbaroosa.
Amazingly Embarrassing Parents: In episode 25, Marika has the chef transmit a message to the other pirate ships regarding where the final fight is going to take place. The song playing in the background is the pirate song, with an extra addition of girls singing a bit off-key. Kenjo, upon hearing it, tells one of his crew mates to broadcast it across the entire ship. Chiaki is then shown hiding under the covers of her bed, and a short cutaway scene shows her and Marika recording the song being broadcasted. Marika, on the other hand, smiles proudly and seems to enjoy the song.
Not to mention that he tells Marika that she is Chiaki's favorite pirate.
The Lancer: He seems to serve as one for Marika during the Grand Cross arc, as he's something like her second in command as far as the fleet is concerned.
Reasonable Authority Figure: Like Ririka towards Marika, he gives Chiaki a surprising amount of freedom. A large part of it is mostly to ensure Marika's safety, but he also has no qualms with letting Chiaki fill in for Marika while the latter searches for the ghost ship with Gruier.
Voiced by: Eizou Shuda (Japanese)
Jenny's uncle and the head of Hugh and Dolittle Interstellar Transportation.
Large Ham: Has a penchant for making dramatic entrances; his first appearance is standing ontop of his ship, dramatic wind blowing his cape behind him (it's actually a projected hologram) and adding sound effects to weapons fire. He also steals Quartz's thunder right out from her when she's making her big speech to the pirates.
A famous Chinese chef whose restaurant served as a meeting point and base for the Sea of Morningstar original pirates. His sons (two of whom we've seen in the series) are running a chain of restaurants around Tau Ceti space which serves as a pirates' secret communication network.