Haruko is an alien named Haruha Raharu (by moving one syllable to the left and adding -ko, you get Haruhara Haruko) who comes to earth on a personal mission. She is out to free a most powerful alien named Atomsk from the clutches of Medical Meccanica, solely because she is in love with him.
Haruko is not quite your normal "anime babe." She has orange (sometimes pink) hair and yellow-green eyes, and a somewhat nasal voice, which is a nice sized jump from the "hot anime girl" cliche, but she still pulls it off. She wears a few odd costumes during the course of the series, but is never seen without the shackle on her wrist. On it is a metal piece that reacts whenever Atomsk is close. It is symbolic to her attachment to him, and the fact that she is a prisoner to her desires; anything she does is solely working toward her one goal and nothing else.
She also speeds around on a yellow Vespa scooter with her bass guitar, which serves mainly as a weapon and also as a gun, a flying transport and an instrument. She claims to be 19, but it is never confirmed if this is her real age. Perhaps she is 19 in alien years? Her favorite food is curry, the spicier the better.
Her character is mischievous and tricky - for those around her, it becomes hard to tell what is the truth and what isn't when she talks. She says such ridiculous things all the time, that when she is actually honest, it is either dismissed ("[I'm] an alien." Episode 1) or accepted without question ("I realized I just have to have your head." Episode 6). While she seems to be the helpful type, she is the most self-centered being alive. She takes up a job as a maid only to neglect any and all housekeeping duties - and only someone like her could get away with it. While she seems to be a heroine that comes to the rescue when danger is afoot, she only does it because it'll bring her one step closer to her goal.
Haruko comes to Earth on her mission to free Atomsk, only knowing that she can do so by getting him through an N-O (hyperspace) channel. She does make a few mistakes and put herself into some risky situations, but plays it all off with a confidence that makes her all the more attractive (and annoying to some of the cast).