I Transmigrated into an Old-School Romance Novel as the Heroine [Ancient Setting]

[An ancient-style version of the novel of the same name, where the heroine transmigrates into an old-school romance novel~] Kuaixue is a very wicked little girl. She loves acting, is wild and free, and is mischievous and clever. One day, she accidentally binds herself to a System and transmigrates into different novels. In the first world, she becomes Tang Kuaixue, a haughty darling of heaven, but this is a novel where she's bound to a System and will die if she doesn't win over the male lead. Kuaixue: "..." System: "..." World System: "…" There can't be two Systems in one world. Kuaixue gleefully asks, "System, can you beat this native?" The System proves its strength, kicking out the World System, which had been shouting about punishing her with electric shocks. It kicks it right into the male lead's body. The heir to a marquisate, who had been lying low and pretending to be a mute coachman while hiding in the richest family's household, suddenly hears a voice in his head. [Mission: Win over Tang Kuaixue] [Reward for success: A delicate, soft body, a natural fragrance, and a fertility pill. Penalty for failure: Death] The heir: "?" In the second world, Kuaixue transmigrates into Qi Kuaixue, an unfavored princess of a fallen kingdom. As a child, she pledged her love to the neighboring kingdom's crown prince over a jade pendant, only to be bullied after a supporting female character took her place. In the end, her heart turned to ash, and she jumped from the city wall. When Kuaixue arrives, it's her wedding night. The crown prince lifts her veil. In the original story, this is when he'd say a whole lot of nasty things. Kuaixue can guess what he's about to say, so she simply pushes him down first. The next morning, the supporting female character shows up, taunting her. "Big Brother Crown Prince didn't touch you last night, did he? You need to know your place--" Kuaixue glances sideways at the male lead. "Did he touch me or not...?" The male lead, who has suffered every humiliation and wants nothing more than to get rid of Kuaixue, but has to endure it all in fear that she'll say something: "Don't be rude to the crown princess..." Supporting female character: "?" [Thanks to my friend for the inspiration. I might add these later.] ① A young widow whose husband dies soon after their wedding. To ensure the family line continues, her in-laws secretly have the stern, cold male lead's older brother father a child with her. ② A doctor living deep in the mountains saves the nearly dead male lead. His way of repaying her is to marry her as a concubine (the version where she turns the tables on him). ③ ... [Reader's Guide | Content Warnings] 1. Gender-bender story, includes male pregnancy. 2. More details will be added before the novel begins. Theme: Love is a powerful force