Here's where I'm going with her so far:
Rin's origins are a mystery. She was abandoned at the gates of a remote monastery not long after her birth. As is the custom, the monks took her in and did their level best to raise her according to their tradition, even after it was plain and clear that this strange little girl with her white hair and jade-green eyes was too restless and wild at heart to make a proper nun. By the time she was four, only one of the monks was still willing to spend time and effort on her. One day, on a whim, he showed her the first movements in a beginning kata in Tiger and Crane style...and to his delighted surprise found that he had a new prodigy on his hands. From that day forward, Rin trained when she was not doing chores, sleeping, or eating. She soaked up new moves and techniques like a sponge, delighting in her skills. She paid rapt attention to Master Tso's lectures on the duty of a martial artist: defend the weak and helpless, uphold justice, and do no harm where it could be avoided.
So her life continued until the sad day when Master Tso, her mentor and father figure, passed on. Within an hour, the Abbot swept Rin aside and quietly advised her that he had left two things for her: first, his personal manual of martial arts lore from a family style; and second, a letter of introduction to a man who owed him a life favor. That night, Rin left the monastery for the wider world.
Some months later, she finally found her master's friend in a graveyard in Hong Kong. By chance, his sons were visiting his grave and were willing to honor their father's obligation to the old monk. One of them was moving to America shortly for business reasons and offered to 'adopt' her. She did not think to argue with her good fortune...nor ask what manner of business the man might have.
Thus, here she is, a world away from the tiny monastery, wide-eyed and curious at all the wonders around her. At first glimpse, she is but an innocent lass late to bloom...but total immersion has brought her English up to speed with ruthless efficiency and she is only too well aware that she does not fit in here any better than she did back in that quiet monastery. As she grows up, she is becoming aware of a growing rage within at the petty injustices of the world.
Rin is a rather direct person. She is also prone to interpreting things literally: sarcasm and puns are two things she simply does not understand. Her preference is to resolve any dispute politely and without fuss, but if etiquette does not work (as it usually doesn't), 'reasonable' force is permitted. What she considers reasonable can be frightening to innocent bystanders!