Frost Hidden in the Sword Tassel

Shen Jinghan is Bai Yujing's sharpest blade. Her master raised her for twelve years. For ten of them, she killed people on his behalf. She never asked questions. Until one night, she found a copper button on a corpse. It was identical to the one on her sword tassel. She asked her master why. He said, "You don't need to know." For the first time, she didn't sheathe her sword. And for the first time, she didn't call him Master.