Dominion Absolute: Crown of the Invincible

Ginny Lynn does not want to marry a man she has never met, arranged by her family at the request of his mentor. When Teddy Champ arrives from the mountains, talking like a farmer and looking at her in a way she finds crude, she treats him with open contempt. Her grandfather is dying by then, and the doctors in the city have already told the family there is nothing more to do. Teddy treats the old man himself, using medical methods nobody in the household recognizes, and her grandfather recovers. After that, threats keep coming at Ginny from different directions, rivals, debts, men who think she is easy to push around, and each time Teddy deals with it, showing fighting skill that does not match his appearance at all. Ginny stops looking down on him. A woman who trained under the same mentor as Teddy, a junior of his, later confronts Ginny directly. In the clash between them it comes out that Ginny has a rare physical constitution, one built entirely of yin energy. Tracing that constitution back leads to the truth that Ginny was abandoned as an infant by one of the capital's top families.