Remember Self-Control: Bossy Husband Loves Me Deep to Soul - Chapter 10: She Is the Murderer.

In her past life, Michelle was an ordinary doctor who worked in a small hospital, but once in a while, a strange envelope would arrive at her apartment and she would take up a weaon and turn into a deadly assassin known for her stealthiness. But being a top assassin, Michelle had many enemies and ended up dying, only to wake up in the body of Michelle Grace, a pampered young miss in a world similar to ancient dynasties, except that cultivation existed there. Not everyone could cultivate, but Michelle Grace could.The original Michelle Grace was engaged to the Crown Prince, and he killed her before Michelle took over the body, so after making a deal with Michelle Grace's father, the Archduke, Michelle took on the name Grace and started a revenge plan on the Crown Prince, his lover, his mistress and his father, the Emperor.A bit troublesome: Michelle gained the attention of two men who together were the Dark Lord. They were horrifyingly powerful, so Michelle had to be careful around them. Luckily, they didn't have in their plans harming her, as they were intrigued by her constitution. Michelle possessed a rare blood, which they could use.

As a promise, he went out into the world as an assassin. 3 years later, after becoming the Supreme Assassin, he gave up on everything he had and returned to the ranks of ordinary people. But one day, Kismet, a mystical game created by the National Research and Development had appeared.

Enigmatic hands, spectral frame, and one cunning strike just like the swing of the Grim Reaper. The Supreme Assassin takes on the mystical world, and how his legendary tales sets off, progressively ascending the altar to becoming the best.

- Description from Novelupdates

Going against the heavens, Tuoba Ye reincarnated. Body concealing Divine Root, hands holding Divine Talisman, possessing previous life’s experiences, from childhood, began cultivating the most difficult body refining method: Mythical Nine Transformations.

- Description from Novelupdates

The main character is reborn as a character from a game he played in his previous life. This character falls into ruin along with the villainess, spending the last of their years together. A man named Kururi Helan.