This manhua is about a world where yin gives birth to children and yang fights to protect their families. It starts off with two yin siblings one with distinctive blue hair and the other with a bluish tint, I think. They are servants working at a household.
One day, the sibling with distinctive blue hair is sold off to another family, separating the two. She is mistreated in that household until, one day, a black-haired stranger helps her escape. She has multiple flashbacks of this stranger and finds out she has met him before when younger. She returns to her old household, only to find that her sibling has disappeared, taken away. She asks the stranger to help her find her sibling, and protect her along the way. Somewhere along the way, she remembers that she met the stranger before.
Also, at a market, they find a baby tiger, who is lost. I don't remember much from here, but I'm pretty sure the baby tiger was the child of her other sibling she was trying to find, because her sibling married a yang with the power to transform into a white tiger.
If I remember correctly, the manhua was in full color. That's all I remember.