Transmigrated as the Fake Crown Prince, I Rule the Great Sheng

Sheng Tian, a top modern agent, unexpectedly transmigrates and wakes up in the Crown Prince's bridal chamber, only to find the original prince has just died! The frantic Crown Princess discovers he looks exactly like the prince and, to protect her family, forces him to take the prince's place. From then on, Sheng Tian becomes the 'fake Crown Prince' of the Great Sheng Dynasty. He thought he'd be second only to the emperor and live a carefree life, but instead he faces dangers at every turn. The emperor plots against him, brothers scheme, treacherous ministers lurk in court, venomous women set traps in the harem, enemy forces press on the borders, and feudal lords stir unrest. Armed with modern wisdom and ruthless tactics, Sheng Tian holds beauties in one hand and the realm in the other: 'Since I'm wearing this dragon robe, this vast land is mine to rule!' — Description from novelcodex.org