After getting drunk, a modern profligate Xiao Yan accidentally crossed over and became the ninth prince of the Dayuan Dynasty, who was bullied by everyone. As soon as he opened his eyes, he was framed by the crown prince's faction for embezzling disaster relief silver and was about to be thrown into the celestial prison. Relying on modern commercial thinking and the original owner's memory, he took out the account books in court, exposed the truth of the crown prince's corruption, and was approved to establish the Debt-Clearing Bureau. Since then, he has recruited talented people from the streets, investigated the debts of powerful nobles, founded a royal club, and used commerce to raise grain and provide disaster relief; he also established newspaper offices, built trade routes, reformed the imperial examinations, and promoted mutual markets, wielding the means of statecraft under the appearance of eating, drinking, and making merry. Facing the crown prince's seizure of power, border wars, and foreign invasions, Xiao Yan used account books as his proof and trade routes as his game, ultimately pacifying internal rebellions, stabilizing the frontiers, and ascending the throne.