Nine Clouds Ember

The Female Protagonist Goes to the Countryside, Her Parents and the Male Protagonist's Grandfather Are Sent Together, and the Male Protagonist Is a Soldier

I am looking for a period novel that I have read. I forgot to add it to the bookshelf at the time. The character is that the heroine takes her younger brother to the countryside. The heroine is good at ancient martial arts and has inner strength. She can hit people with small stones. The hero is a soldier. He visits his grandfather in the cowshed and lives in the heroine's house in the name of her cousin.