She is the 2nd youngest of the Doryu children.
At 16 years old, her assassination skills were so good that even her siblings became wary of her.
Because she's been raised to act as a killing machine for the Doryu Family, she lacks the capacity to interact with her other siblings and express her feelings normally. Although she has shown interest in the youngest it is unbeknownst to everyone.
As precaution the Patriarch sent her away at a young age to train under the most famous and dangerous place filled with assassins where she quickly rose to one of the top spots.