Sapphire

She is, even at her young age, a high ranking member of the army, technically. But usually she doesn't care and prefers to read books, theorize about magic or study the stars. If it wasn't for her magical prowess, which is more impotant in her country than a military rank and equal to a social status, she would have already gotten a lot of harsh punishments.
With her hobbies she normally stays at home, but even when she has to go outside, her apparance doesn't matter to her. As long as it's comfortable and more or less functional it'll work for her.
Since she basically doesn't care about anything but her hobbies, it may be surprising that she tries to pay her depts if she owes something to someone.
Additionally she has a very selective memory and tends to forget things she thinks aren't important.

Concept Artwork