Content warning: The leads are both virgins at first, but later the heroine becomes emperor, so... there is a pseudo-incest plotline later on.
When she was ten, Princess Yuanhui Li lost her mother and nearly starved to death in the Cold Palace.
A young man in blue robes often came to see her, bringing her food and drink and telling her about the world beyond the Cold Palace.
After she left the Cold Palace, he came to her rescue again, even at the cost of offending the emperor's beloved Third Princess.
When Yuanhui Li first entered the world of power, she was treated as a pawn and betrothed to the Yuwen clan.
Fortunately, the man she married was the young man in blue robes she had always longed for.
After their wedding, they were perfectly in tune, affectionate and harmonious, inseparable as glue.
When the young man's entire clan was executed, she stopped being an obedient daughter for her husband's sake. Before her suspicious father, the emperor, she personally slew the imperial guards.
She gave the young man her whole heart and, wanting him to be able to protect himself, appointed him commander of the guards defending the imperial city.
But she never imagined he would rebel against her.
Overnight, their positions were reversed. He became the supreme emperor, and she became a prisoner...