Magika no Kenshi to Shoukan Maou - 3.1.1 — The Night of Beginning

Bai Aoxue, the best mercenary in the 21st century, is accidentally sent back to the Chengxi Dynasty in Great Continent due to an explosion in her mission, and trapped in the first daughter of Prime Minister. After her rebirth, she is set up by her father to marry the 5th prince Jun Yeyan who wears a mask all day long.
In the face of bloodthirsty enemies, discord between brothers, collusion among courtiers and invasion of enemy state, can Bai and Jun resolve the crises? What will happen to their political marriage? How will the fierce battle for the throne end?
With many twists and turns, the book brings you to experience palace revolution, love and hatred thousands of years ago.

- Description from Novelupdates

Though it may be a dream weathered, crumpled, fading,I held on without surrender.Through each repeated day, running toward tomorrow’s light,I became a knight, resolute and bright.

Rosemary spent 18 years thinking she was a member of the wealthy Harris family, only to discover she was a fake rich girl. When the real heiress returned, Rosemary was cast aside and sent back to her poor hometown. But fate had other plans for her, as she soon discovered that her hometown was actually the most exclusive villa area in the country. In a single night, Rosemary went from a modestly wealthy girl to the true heiress of a top-tier elite family. Her biological parents showered her with love, handing her millions of dollars in pocket money, providing access to any car from their fleet, and letting her buy anything from the world’s top designers. As for school, the best institutions were at her fingertips, and if she didn’t feel like studying, she could play with the family company.But what shocked Rosemary the most was finding out she had an ex-fiancé. She couldn’t understand why he kept clinging to her, holding her hand, and trying to kiss her. “Who are you, sir?” Rosemary asked, annoyed. “Sweetheart, I’m your husband,” the ex-fiancé responded. “I don’t have a husband, only a former fiancé”

The world’s top level hacker, Shi Lei; due to him hacking the world’s top military powers during a joint exercise and attempting to steal information from them, ultimately leads him to get sold out by his own organization. This act eventually caused his own death by a missile bombardment.

God was playing a joke on him and allowed him to return back to six years ago, the autumn season of when he was still at his university. Being given another chance, plus the fact that he retained his ability as one of the best in hacking technology, Shi Lei decided to change his life! During his previous life, he was only an assassin in the dark. Although such an existence made people afraid of him, he would have to always hide within the shadows. In his new life, not only does he want to be an assassin in the dark, he also wants to stand openly in the middle of the world stage. Creating a world-class super enterprise, he will single handy change the whole world!

- Description from Novelupdates