MTL - Endless Dantian - Chapter 6 Little brother?

After the real daughter of the Jiang family fell sick, she became stupid and insisted on marrying the cold-blooded, cruel, and crippled Fu Jiu. Mother Jiang said, "So be it. She's a good-for-nothing anyway. I only asked her to marry in place of my sister." Father Jiang: "After you marry him, remember to ask 9th master to help your sister find a better marriage." The fake heiress said, "Sob, I feel so sorry for Sister, but… if you get beaten to death by the 9th master, the Fu family will compensate us a lot of money, right? I'm looking forward to it." Jiang Li sneered. She bid farewell to her hypocritical family and brought her shabby dowry to the Fu family. After having been reborn once, she knew very well that Fu Jiu was the only person who treated her well. Everyone was waiting for Jiang Li to be beaten to death. Finally, one day, she was photographed by reporters and posted online. "It's all your fault! You used so much force last night! The Jiang family is going to laugh at me again!" Fu Jiuxiao said, "With me around, no one will dare to laugh at you. Moreover, I will make them pay back tenfold for the pain that the Jiang family has caused you!"

This book narrates the joyful cultivation tale of an ordinary commonplace university student and a cute and coquettish little fox.

Eight hundred years ago, Xie Lian was the Crown Prince of the Xian Le kingdom. He was beloved by his citizens and was considered the darling of the world. He ascended to the Heavens at a young age; however, due to unfortunate circumstances, was quickly banished back to the mortal realm. Years later, he ascends again–only to be banished again a few minutes after his ascension.

Now, eight hundred years later, Xie Lian ascends to the Heavens for the third time as the laughing stock among all three realms. On his first task as a god thrice ascended, he meets a mysterious demon who rules the ghosts and terrifies the Heavens, yet, unbeknownst to Xie Lian, this demon king has been paying attention to him for a very, very long time.

- Description from Novelupdates

This is a story of a man named Kim Sae-Jin, who one day, inexplicably wakes up as a Monster. Follow him and his perilous journey to get his life back as a Human, all the while growing even more versatile as a Monster in the process. This should be… complicated, somewhat.