The Crown Prince of Great Zhou

Zhou Ning transmigrated into the body of the emperor's eldest son and thought he was Heaven's chosen one. Then, to his dismay, he discovered he wasn't born of the empress. The crown prince was always chosen from among the legitimate sons, not simply the eldest. Fine, he wouldn't compete. He'd be a carefree prince instead. But the identity of the emperor's eldest son was far too sensitive for Zhou Ning to live carefree. In that case, I'll just have to make a reluctant bid for the crown prince's position...