Amelia Thornheart - Chapter Sixty-Nine: Moonrain

Leon, a man who tragically died of exhaustion due to his sister's otome game, unexpectedly finds himself reincarnated as a young aristocrat named Leon Bartfort. However, he soon realizes that he is not alone in this body. Another mysterious entity already resides there, its voice echoing in his mind.Who is this second consciousness? Is it a friend, an enemy, or something far more sinister? Will they be able to come to an agreement to share control over the body, or will a fierce struggle for dominance ensue? Or perhaps their interactions will lead to unforeseen consequences?Intrigued? Then start reading!

In novels with a stud there is always a Senior Martial Brother like this:

In the early stages of the novel, his innate talent is high, his cultivation is good, his appearance is handsome, and he has an intelligent, cute younger Martial Sister as a fiancée.

In the middle stages of the novel, he is caught unprepared and defeated by a young disciple (the protagonist) in the sect who’s hardly remarkable at all. From then on, he falls from his godly altar and loses his brilliance. Even his young Martial Sister leaves him for someone else.

In the late stages of the novel, he continues to turn dark, going down the Demonic Path and becoming the major villainous boss. However, the protagonist still ruthlessly defeats him and his soul is eternally sealed.

Once Qin Mo opened his eyes, he discovered that he had become this Senior Martial Brother.

- Description from Novelupdates

The MC entered the body of the An family eldest son, An Ziran, an arrogant 16 years old boy who weighed 78 kg (~171-172 lbs), who only knew how to eat, play and sleep. Seeing his current body, An Ziran decided his first priority was to LOSE WEIGHT!

Three days later after he became An Ziran, An Ziran’s father and his biological mother died, which meant as the eldest son he had to take over the family business.

Beside his legitimate first wife, An Ziran’s father also married 3 others women, who all wanted to take over the An family fortune but only the eldest son could be able to touch it, therefore they have to depend on An Ziran in order to live a comfortable live.

An Ziran’s father also had an older brother who is always planning to steal the An family fortune. The elder brother of An Ziran’s father and the woman he married had powerful connections. In order to save the An family fortune, An Ziran has to find a golden thigh to cling on. The butler told An Ziran that there is an engagement between the An family and an influential family. Therefore he takes his sister to that family house to make a connection.

However, during their journey, An Ziran’s younger sister overheard that the son of that family is UGLY, so as a beautiful and spoiled young lady coming from a rich household, she didn’t want to marry him and decided to run away. Without any other choice, An Ziran had to take his sister’s​ place and marry that man, who told him that he would let him go soon, but lied.

- Description from Novelupdates

Everyone must have a few regrets in their lives, and for Mykel regret was publishing this novel on the internet. Because of this failed novel he wrote, made his career down the hill as an author. Thanks to this novel, he lost his passion and he lost everything that he had.

"I wish I can destroy this novel so that nobody will be able to see it or remember it anymore," Mykel said.

That was what he wished for, and for some reason, he went inside that novel of his and as himself in the story that didn't suppose to exist?

Mykel smirked and grinned as he looked at the system.

[You are the creator of this world, you will have the access to the command system. You are free to do anything as long as it is listed in the command system]
[Please enjoy and have fun]

"Heh, then I will turn this world upside down," Mykel said as he glared at the notification in front of him.