I Killed My Scumbag Husband, Only to Learn My Younger Brother-in-Law Was a Monster in Fine Clothes

[Not mutually exclusive! Not mutually exclusive! Not mutually exclusive! + puppy-like, sweet-on-the-outside-black-on-the-inside younger brother] Lan Ling is low-born but stunningly beautiful. When her younger brother is gravely ill and she has nowhere left to turn, a strikingly handsome man comes to her aid, saving both her and her brother. He promises her a lifelong partnership, with no one else between them. Three months later, when the Crown Prince of the Eastern Palace takes a principal wife, a palace matron comes to fetch Lan Ling. Only then does she learn that the husband she thought she could rely on for the rest of her life is the Crown Prince himself, and that she is merely the lowest-ranking among his many concubines. She once believed she was special to the Crown Prince. But he goes from neglecting her to doubting her, and eventually even causes the death of the person dearest to her! Her heart turns to ash, and she comes to hate him to the bone. At last, she steels herself to stab the Crown Prince to death. But the entire scene is witnessed by the Crown Prince’s younger brother, the Sixth Prince! She never could have imagined that beneath the innocent exterior of this always-sweet younger brother-in-law lurked a beast in human clothing.