Tang Dynasty: Starting at Xuanwu Gate, this prince is better off not being one.

He only wanted to live a peaceful and wealthy life as a prince! Why are there always scoundrels forcing him to perform meritorious deeds?! Li Yu was originally a salesman at a pharmaceutical company in the 21st century. By accident, he transmigrated to the early Tang Dynasty in a parallel world and became a disciple of Sun Simiao. At this time, the Tang Dynasty had been renamed "Zhou" by its founder, Li Yuan, and the historically deceased Li Xuanba had become his father. Salt production? Ice production? Gunpowder? A clash between cold weapons and modern technology? Grasslands? Turks? Tuyuhun? Leading the Tang cavalry to the plateau? Facing an unknown future and a historical trajectory slightly different from the original, Li Yu, who had just escaped from the Qinling Mountains after many hardships, was forced to accompany Li Er in a battle against the Crown Prince's faction at Xuanwu Gate…