Board Thread:General Discussion/@comment-3257939-20131104060426/@comment-82.12.156.248-20140105191936

BenRG wrote: This is just an idea but I think this is Yang's oath to Ruby. She's promising to keep her little sister safe and happy no matter what happens.

Keeping with this: We haven't actually been clued in to Yang's motives for becoming a huntress:

Ruby wants to help people and, ebign the 15 year old she is blinded by the romance and adventure; Weiss is seemingly doing so either because she is rebelling against her family, hinted at by her numerous characteristics OR is training to combat the White Fang threat to her family (unlikely since she seems more tolerable of Faunuss at the end of Black and White and that she never actually directly engages White Fang members [though I'm willing to bet that will change in Volume 2); and Blake is becoming a huntress because she has the abilities too and because it's not only a better use of her abilities than serving the White Fang but I think she personally feels like this is a way of redeeming herself for her past crimes and hopefully bringing Faunuss back to prominence in an alternative manner.

However we get no clue in about Yang's motives just that she is becoming a huntress. Perhaps Yang is doing so for the sole purpose of protecting Ruby following Ruby's mother's death and her father accepting her back into his life. (In my opinion it seems that they are half sisters, sharing a father. Following the death of Ruby's mother Yang's family (Ruby half-family.. if that's even a thing...) accepted her back in and Yang swore to protect her with her life due to whatever may have been out to kill Ruby and her mother still being alive.

It definately plays off as Yang singing an old lullaby to Ruby, and it does seem very possible since Ruby does hint that it used to be Yang who acted as her mother following the death of Summer, it's not entirely surprising that Yang may have sung lullabies like this one to her if Ruby was ever scared.