Fleed Maria Grace

Japanese name:

グレース・マリア・フリード

Duke Fleed's tomboyish younger sister, raised by her family's butler on Earth after the destruction of their native planet. She appears late in the series and falls in love with Koji; it is hinted he is attracted to her as well even though they never stop arguing, but at the end of the series both she and Duke return to space to rebuild their homeworld.

Wikipedia