The Tang Empire of Cavalry and Cutting

World view: The continent of Calradia (510 million square kilometers, 10 billion people) is divided into six major powers-Vlandia, Battania, Sturgia, Kuset, Aselei, and the Empire. Protagonist: Jin Yin, a time traveler, was originally a graduate student in the Department of Modern History. He is familiar with the history of the Tang Dynasty and "The Art of War". He starts as a down-and-out little lord. Female protagonist: Rong Juan, originally a female warrior of the Batania tribe, was later conquered by Jin Yin. She is proficient in riding, archery and intelligence, and has a cold and decisive personality, becoming Jin Yin's right-hand man and soul mate.