My Space-Time System - Chapter 14: Understanding.

When our protagonist becomes the game character Jun Karentia, she thinks she has it made. She may be just a lowly support mage, but with her knowledge of the game, she knows she can finagle her way to the good ending following around the main character, Fabian. The problem? This game doesn’t end after one playthrough. Jun is prepared to guide Fabian through the second playthrough to the true ending when… Fabian abandons her. Now the Grand Duke Mayer Knox—captain of the Dark Knights and the secret final boss—is determined to have her join his party. Can Jun turn the final boss into the main character? Why is Mayer Knox so intent on having her in his party? And when will these rumors about being his lover stop?!

After ten thousand years of cultivation, he could have achieved immortality. However, his lack of human experience led to his failure to attain immortality.Thus, he resolved to immerse himself in a century of human existence, seeking to enhance his journey toward immortality. What he didn’t anticipate, though, was that upon entering the human world, he would find himself cast as a son-in-law, facing disdain not only from his wife’s parents but also from his beautiful wife herself.Armed with a wealth of cultivation knowledge, how could he transform his drab human life?

The older young Lisko woke up and found that he had become an American. He took over his father’s ranch and began to live in the United States.

- Description from novelbuddy

This is a ‘rebirth’ story where Chen Rong, the heroine, finds her second chance at life after burning herself to death. Set in the Eastern Jin era when bureaucrats and their lofty yet equally hypocritical and oppressive ideas once ruled the empire, Chen Rong is made to use her past life’s experience to survive and hopefully find happiness this time around.