|Family|| Soichiro Yuki/Wataru Yuki (Father),|
Fumi Yuki / Kanna Yuki (Mother)
Goro Yuki / Captain Harlock / Susumu Kodai (Uncle)
Mamoru Yuki (Younger Brother)
Manabu Yuki (Younger Brother)
Kei features the standard appearance of young female characters by Leiji Matsumoto, a young woman with a willowy body, long eyelashes, sparkling brown eyes, and long blonde hair (although Kei's hair is often shorter compared to other character's). She is usually dressed in a primarily pink jump suit with a black collar that features a skull and crossbones, black bloomers, black boots with white tops, and white gloves.
Kei is a strong and doughty young woman who from her many years seeing the deteriorating state of Earth and her time with Captain Harlock has become determined to spend life they way she wishes too. Disgusted with how Earth's political state has become, especially with how she lost her parents because of them, Kei joined Captain Harlock hoping to gain her freedom.
Kei is noted to have a strong admiration for Harlock for giving her a better chance at life to the point where she even has some romantic inclination towards him. While having a rocky start when Tadashi Daiba had first joined, she eventually begins to warm up to him as a crew mate and depending on the series borders on being more than friends or potential lovers. She also has a good relationship with the rest of the crew, spending most time with Yattaran.
Years of experience under Captain Harlock has made Kei a capable and ready fighter and pilot. Her experience in using the radar has allowed Kei to predict how an opponent will attack and from where. As a pilot, Kei is more than capable of piloting a Wolf and even steer the Arcadia.
Due to the loose canon of the Leijiverse, Kei's background is best described as complicated. All series she appears in describes her as an orphan who for various circumstances had lost her parents in an event that was ignored by Earth's government. After which she was put under the care of a guardian until losing him as well. Around an unspecified point, she encountered the Space Pirate Harlock and joined his crew, eventually becoming a trusted crew mate. Her first appearance was in the manga Miraizer Ban.
Kei's surname Yuki roughly translates to 'Existing Record' referencing Kei as proof that her parent's lived and did not die for nothing as was put up by the lazy politicians of Earth. Yuki itself is a common name for female Japanese characters by Leiji Matsumoto. Her given name translates to 'firefly', which in Japanese lore is seen as a symbol of passionate love, altered forms of souls dying in war, and a guiding light; all of which describe Kei's desires and stance as part of the Arcadia's crew particularly with Tadashi.