Haruka is a
really boyish girl who likes car racing and motorcycles.
She supposedly lives with Michiru in S and, in
SailorStars with her and Setsuna taking care of Hotaru as
Haruka-papa. (!) In the Anime you don't hear about her
family.
Haruka, plus her motor sports, plays piano making a duet with Michiru. She, even without saying, has a love relationship with her. It is demonstrated in how jealous she is about her been with other guys... When she first appeared, Minako and Usagi thought she was a boy, so followed her, till they discovered the truth. She's ambitious and sort of arrogant, but quite sensible some times. (When Michiru's talisman is found, when she dies in SailorStars, etc.)
Her name means Distant Sky Ruler and her planet in Japanese is called Sky King Star. Even though, her powers confuse, because her main attack is World Shaking. But her attacks with her talisman, the Space Sword, relate to heaven or sky. In SailorStars she transforms into Super Sailor Uranus.