It's less about romance and more about a brutal, political chess game, honestly. The 'romance' often springs from that tension—power imbalances so severe any affection feels like a miracle, or a calculated lie. Think of the emperor in 'The Legend of Zhen Huan' or countless webnovels; his love is a weapon, a reward, and the ultimate vulnerability. The consort's love is her survival strategy. Real tenderness, when it appears, is almost subversive.
What defines it for me is the inherent loneliness. Even in fluffier stories, the emperor can never be just a husband. There's always the crown, the harem, the court watching. The dynamic revolves around navigating that gulf. Does she carve out a private space within the palace's gold cage? Does he, for her, momentarily forget he's the Son of Heaven? That moment of forgetting is the entire point of the genre, I think. The good stuff makes you believe, just for a chapter, that it's possible.