Where to find the clear shadow tonight

Weapon designer Qin Luoyan dreamt she was transported to the Southern Yue Kingdom, becoming the unfortunate second young lady of General Qin's family. Though delicate and frail, she was oppressed by a powerful figure, forced to marry an old man old enough to be her father in exchange for benefits. Not one to be a proper young lady, she naturally sought every means to escape this marriage. Taking advantage of the reputation of Prince Xuanwu, Fu Ziming, a frequenter of brothels, she had a one-night stand with him, achieving her goal of escaping the marriage. She thought the world was her oyster, but little did she know that Prince Xuanwu was like a persistent leech, impossible to shake off.

Synopsis from DramaGo.