You Were Supposed to Be the Emperor's Stand-In, So How Did You End Up Ruling the Empire?

He transmigrates and becomes a stand-in for the emperor of the Great Qian Dynasty! What? The emperor indulged in pleasure when he was young and ruined his health, so to secure the throne, he wants the newcomer to sneak into the empress's chambers and father a child in her womb? And what's more... the empress has remained a virgin, even after three years of marriage! As a modern-day wage slave from the 21st century, Ye Chen knows that once the mission is complete, he'll be killed too! He strikes decisively and turns the tables! He conquers the beautiful empress and the aloof empress dowager! He slays the scheming eunuchs and the violent Emperor Qian! Within the realm, I am the law. Disobey my orders, and die! Beyond the dynasty, foreign nations and peoples eye our lands hungrily. Anyone who dares lay claim to the Great Qian throne will die! What, a stand-in emperor? I'm the one and only true dragon of Great Qian!